start with RTC for G0

2025-12-06 02:35:23 +03:00 · 2023-01-12 23:29:30 +03:00 · 2023-01-12 23:29:30 +03:00 · 5066fcf3c2
commit 5066fcf3c2
parent b1c8012e11
20 changed files with 1221 additions and 0 deletions
--- a/G0:G070/RTC/Makefile
+++ b/G0:G070/RTC/Makefile
@ -0,0 +1,164 @@
+BINARY		= rtc
+BOOTPORT	?= /dev/ttyUSB0
+BOOTSPEED	?= 115200
+# MCU FAMILY
+FAMILY		= G0
+# MCU code
+MCU			= G070xx
+#DEFS		= -DEBUG -g3
+# change this linking script depending on particular MCU model,
+# for example, if you have STM32F103VBT6, you should write:
+LDSCRIPT	= stm32g070xb.ld
+
+INDEPENDENT_HEADERS=
+
+FP_FLAGS	?= -msoft-float
+ASM_FLAGS	= -mthumb -mcpu=cortex-m0plus -march=armv6-m -mtune=cortex-m0plus
+ARCH_FLAGS	= $(ASM_FLAGS) $(FP_FLAGS)
+
+# autoincremental version & build date
+VERSION_FILE = version.inc
+ifeq ($(shell test -e $(VERSION_FILE) && echo -n yes), yes)
+    NEXTVER := $(shell expr $$(awk '/#define BUILD_NUMBER/' $(VERSION_FILE) | tr -cd "[0-9]") + 1)
+else
+    NEXTVER := "1"
+endif
+
+BUILDDATE := $(shell date +%Y-%m-%d)
+
+###############################################################################
+# Executables
+PREFIX		?= /opt/bin/arm-none-eabi
+
+RM			:= rm -f
+RMDIR		:= rmdir
+SIZE        := $(PREFIX)-size
+CC			:= $(PREFIX)-gcc
+LD			:= $(PREFIX)-gcc
+AR			:= $(PREFIX)-ar
+AS			:= $(PREFIX)-as
+OBJCOPY		:= $(PREFIX)-objcopy
+OBJDUMP		:= $(PREFIX)-objdump
+GDB			:= $(PREFIX)-gdb
+STFLASH		:= $(shell which st-flash)
+STBOOT		:= $(shell which stm32flash)
+
+###############################################################################
+# Source files
+OBJDIR 		= mk
+LDSCRIPT	?= $(BINARY).ld
+SRC			:= $(wildcard *.c)
+OBJS		:= $(addprefix $(OBJDIR)/, $(SRC:%.c=%.o))
+STARTUP		= $(OBJDIR)/startup.o
+OBJS 		+= $(STARTUP)
+DEPS		:= $(OBJS:.o=.d)
+
+INC_DIR ?= ../inc
+
+INCLUDE 	:= -I$(INC_DIR)/Fx -I$(INC_DIR)/cm
+LIB_DIR		:= $(INC_DIR)/ld
+
+###############################################################################
+# C flags
+CFLAGS		+= -O2 -MD -D__thumb2__=1
+CFLAGS		+= -Wall -Werror -Wextra -Wshadow -Wimplicit-function-declaration
+CFLAGS		+= -Wredundant-decls $(INCLUDE)
+# -Wmissing-prototypes -Wstrict-prototypes
+CFLAGS		+= -fno-common -ffunction-sections -fdata-sections -flto
+
+###############################################################################
+# Linker flags
+LDFLAGS		+= --static -nostartfiles --specs=nano.specs -flto
+LDFLAGS		+= -L$(LIB_DIR)
+LDFLAGS		+= -T$(LDSCRIPT)
+LDFLAGS		+= -Wl,-Map=$(OBJDIR)/$(BINARY).map
+LDFLAGS		+= -Wl,--gc-sections
+
+###############################################################################
+# Used libraries
+LDLIBS		+= -Wl,--start-group -lc -lgcc -Wl,--end-group
+LDLIBS		+= $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+
+DEFS		+= -DSTM32$(FAMILY) -DSTM32$(MCU)
+
+#.SUFFIXES: .elf .bin .hex .srec .list .map .images
+#.SECONDEXPANSION:
+#.SECONDARY:
+
+ELF		:= $(OBJDIR)/$(BINARY).elf
+LIST	:= $(OBJDIR)/$(BINARY).list
+BIN		:= $(BINARY).bin
+HEX		:= $(BINARY).hex
+
+all: bin list size
+
+elf: $(ELF)
+bin: $(BIN)
+hex: $(HEX)
+list: $(LIST)
+
+ifneq ($(MAKECMDGOALS),clean)
+-include $(DEPS)
+endif
+
+$(OBJDIR):
+	mkdir $(OBJDIR)
+
+$(STARTUP): $(INC_DIR)/startup/vector.c
+	$(CC) $(CFLAGS) $(DEFS) $(INCLUDE) $(ARCH_FLAGS) -o $@ -c $<
+
+$(VERSION_FILE): *.[ch]
+	[ -f $(VERSION_FILE) ] || echo -e "#define BUILD_NUMBER \"0\"\n#define BUILD_DATE \"none\"" > $(VERSION_FILE)
+	@echo "  Generate version: $(NEXTVER) for date $(BUILDDATE)"
+	@sed -i "s/#define BUILD_NUMBER.*/#define BUILD_NUMBER \"$(NEXTVER)\"/" $(VERSION_FILE)
+	@sed -i "s/#define BUILD_DATE.*/#define BUILD_DATE \"$(BUILDDATE)\"/" $(VERSION_FILE)
+
+# Uncomment and rename file, which includes version.inc
+#$(OBJDIR)/proto.o: proto.c $(VERSION_FILE)
+
+$(OBJDIR)/%.o: %.c
+	@echo "  CC      $<"
+	$(CC) $(CFLAGS) $(DEFS) $(INCLUDE) $(ARCH_FLAGS) -o $@ -c $<
+
+#$(OBJDIR)/%.d: %.c $(OBJDIR)
+#	$(CC) -MM -MG $< | sed -e 's,^\([^:]*\)\.o[ ]*:,$(@D)/\1.o $(@D)/\1.d:,' >$@
+
+$(BIN): $(ELF)
+	@echo "  OBJCOPY $(BIN)"
+	$(OBJCOPY) -Obinary $(ELF) $(BIN)
+
+$(HEX): $(ELF)
+	@echo "  OBJCOPY $(HEX)"
+	$(OBJCOPY) -Oihex $(ELF) $(HEX)
+
+$(LIST): $(ELF)
+	@echo "  OBJDUMP $(LIST)"
+	$(OBJDUMP) -S $(ELF) > $(LIST)
+
+$(ELF): $(OBJDIR) $(OBJS)
+	@echo "  LD      $(ELF)"
+	$(LD) $(LDFLAGS) $(ARCH_FLAGS) $(OBJS) $(LDLIBS) -o $(ELF)
+
+clean:
+	@echo "  CLEAN"
+	$(RM) $(OBJS) $(DEPS) $(ELF) $(HEX) $(LIST) $(OBJDIR)/*.map
+	@rmdir $(OBJDIR) 2>/dev/null || true
+
+size: $(ELF)
+	$(SIZE) -Ax $(ELF)
+
+flash: $(BIN)
+	@echo "  FLASH  $(BIN)"
+	$(STFLASH) write $(BIN) 0x8000000
+
+boot: $(BIN)
+	@echo "  LOAD $(BIN) through bootloader"
+	$(STBOOT) -b$(BOOTSPEED) $(BOOTPORT) -w $(BIN)
+
+openocd:
+	openocd -f openocd.cfg
+dbg:
+	arm-none-eabi-gdb $(ELF) -ex 'target extended-remote localhost:3333' -ex 'monitor reset halt'
+
+
+.PHONY: clean flash boot size openocd dbg
--- a/G0:G070/RTC/README
+++ b/G0:G070/RTC/README
@ -0,0 +1,10 @@
+Simplest work with RTC
+
+Proto:
+
+t - print current Tms
+T - print current Time like 'Mon Jan 1 00:05:19 2001'
+
+
+Button press - print current time @ usart3
+
--- a/G0:G070/RTC/main.c
+++ b/G0:G070/RTC/main.c
@ -0,0 +1,71 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stm32g0.h>
+
+#include "proto.h"
+#include "rtc.h"
+#include "strfunc.h"
+#include "usart.h"
+
+// KEY (intpullup->0) - PC0
+// LED - PC8
+
+volatile uint32_t Tms = 0;
+
+/* Called when systick fires */
+void sys_tick_handler(void){
+    ++Tms;
+}
+
+static void gpio_setup(void){
+    RCC->IOPENR |= RCC_IOPENR_GPIOCEN; // enable PC
+    // set PC8 as opendrain output, PC0 is pullup input, other as default (AIN)
+    GPIOC->MODER = (0xffffffff & ~(GPIO_MODER_MODE8 | GPIO_MODER_MODE0)) | GPIO_MODER_MODER8_O;
+    GPIOC->PUPDR = GPIO_PUPDR0_PU; // pullup
+    GPIOC->OTYPER = GPIO_OTYPER_OT8; // open drain
+}
+
+int main(void){
+    StartHSE();
+    rtc_setup();
+    SysTick_Config(8000); // 1ms counter
+    gpio_setup();
+    usart3_setup();
+    uint32_t T = 0;
+    int sent = 0;
+    /* Do nothing in main loop */
+    while (1){
+        if(Tms - T > 499){ // blink LED
+            T = Tms;
+            pin_toggle(GPIOC, 1<<8);
+            usart3_sendbuf();
+        }
+        if(pin_read(GPIOC, 1<<0) == 0){ // key pressed - send time over USART
+            if(!sent){
+                print_curtime();
+                sent = 1;
+            }
+        }else sent = 0;
+        int wasbo = 0;
+        char *rcv = usart3_getline(&wasbo);
+        if(wasbo) usart3_sendstr("Buffer overflow occured @ last message\n");
+        if(rcv) rcv = parse_cmd(rcv);
+        if(rcv) usart3_sendstr(rcv);
+    }
+}
--- a/G0:G070/RTC/openocd.cfg
+++ b/G0:G070/RTC/openocd.cfg
@ -0,0 +1,89 @@
+# script for stm32g0x family
+
+#
+# stm32g0 devices support SWD transports only.
+#
+source [find interface/stlink.cfg]
+source [find target/swj-dp.tcl]
+source [find mem_helper.tcl]
+
+if { [info exists CHIPNAME] } {
+	set _CHIPNAME $CHIPNAME
+} else {
+	set _CHIPNAME stm32g0x
+}
+
+set _ENDIAN little
+
+# Work-area is a space in RAM used for flash programming
+# Smallest proposed target has 8kB ram, use 4kB by default to avoid surprises
+if { [info exists WORKAREASIZE] } {
+	set _WORKAREASIZE $WORKAREASIZE
+} else {
+	set _WORKAREASIZE 0x1000
+}
+
+#jtag scan chain
+if { [info exists CPUTAPID] } {
+	set _CPUTAPID $CPUTAPID
+} else {
+	# Section 37.5.5 - corresponds to Cortex-M0+
+	set _CPUTAPID 0x0bc11477
+}
+
+swj_newdap $_CHIPNAME cpu -irlen 4 -ircapture 0x1 -irmask 0xf -expected-id $_CPUTAPID
+dap create $_CHIPNAME.dap -chain-position $_CHIPNAME.cpu
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME cortex_m -endian $_ENDIAN -dap $_CHIPNAME.dap
+
+$_TARGETNAME configure -work-area-phys 0x20000000 -work-area-size $_WORKAREASIZE -work-area-backup 0
+
+set _FLASHNAME $_CHIPNAME.flash
+flash bank $_FLASHNAME stm32l4x 0 0 0 0 $_TARGETNAME
+
+# reasonable default
+adapter speed 2000
+
+adapter srst delay 100
+if {[using_jtag]} {
+	jtag_ntrst_delay 100
+}
+
+reset_config srst_nogate
+
+if {![using_hla]} {
+	# if srst is not fitted use SYSRESETREQ to
+	# perform a soft reset
+	cortex_m reset_config sysresetreq
+}
+
+proc stm32g0x_default_reset_start {} {
+	# Reset clock is HSI16 (16 MHz)
+	adapter speed 2000
+}
+
+proc stm32g0x_default_examine_end {} {
+	# DBGMCU_CR |= DBG_STANDBY | DBG_STOP
+	mmw 0x40015804 0x00000006 0
+
+	# Stop watchdog counters during halt
+	# DBGMCU_APB1_FZ |= DBG_IWDG_STOP | DBG_WWDG_STOP
+	mmw 0x40015808 0x00001800 0
+}
+
+proc stm32g0x_default_reset_init {} {
+	# Increase clock to 64 Mhz
+	mmw 0x40022000 0x00000002 0x00000005	;# FLASH_ACR: Latency = 2
+	mww 0x4002100C 0x30000802				;# RCC_PLLCFGR = PLLR=/2, PLLN=8, PLLM=/1, PLLSRC=0x2
+	mmw 0x40021000 0x01000000 0x00000000	;# RCC_CR |= PLLON
+	mmw 0x40021008 0x00000002 0x00000005	;# RCC_CFGR: SW=PLLRCLK
+
+	# Boost JTAG frequency
+	adapter speed 4000
+}
+
+# Default hooks
+$_TARGETNAME configure -event examine-end { stm32g0x_default_examine_end }
+$_TARGETNAME configure -event reset-start { stm32g0x_default_reset_start }
+$_TARGETNAME configure -event reset-init { stm32g0x_default_reset_init }
--- a/G0:G070/RTC/proto.c
+++ b/G0:G070/RTC/proto.c
@ -0,0 +1,83 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stm32g0.h>
+#include <string.h>
+
+#include "rtc.h"
+#include "strfunc.h"
+#include "usart.h"
+
+extern volatile uint32_t Tms;
+
+const char *helpstring =
+        "t - print current Tms\n"
+        "T - print current Time\n"
+;
+
+TRUE_INLINE void putch(char x){
+    usart3_send(&x, 1);
+}
+
+static const char *weekdays[] = {"Mon", "Tue", "Wed", "Thur", "Fri", "Sat", "Sun"};
+static const char *months[] = {"Jan", "Feb", "Mar", "Apr", "May", "June", "July", "Aug", "Sept", "Oct", "Nov", "Dec"};
+
+static void prezero(uint8_t x){
+    if(x < 10){ putch('0'); putch('0' + x);}
+    else USND(u2str(x));
+}
+
+void print_curtime(){
+    rtc_t t;
+    get_curtime(&t);
+    USND(weekdays[t.day - 1]);
+    putch(' ');
+    USND(months[t.month - 1]);
+    putch(' ');
+    USND(u2str(t.day));
+    putch(' ');
+    prezero(t.hour);
+    putch(':');
+    prezero(t.minute);
+    putch(':');
+    prezero(t.second);
+    USND(" 20"); prezero(t.year);
+    putch('\n');
+}
+
+char *parse_cmd(char *buf){
+    // "long" commands
+/*    switch(*buf){
+    }*/
+    // "short" commands
+    if(buf[1]) return buf; // echo wrong data
+    switch(*buf){
+        case 't':
+            USND("T=");
+            USND(u2str(Tms));
+            putch('\n');
+        break;
+        case 'T':
+            print_curtime();
+        break;
+        default: // help
+            USND(helpstring);
+        break;
+    }
+    return NULL;
+}
--- a/G0:G070/RTC/proto.h
+++ b/G0:G070/RTC/proto.h
@ -0,0 +1,22 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+char *parse_cmd(char *buf);
+void print_curtime();
--- a/G0:G070/RTC/rtc.bin
+++ b/G0:G070/RTC/rtc.bin
--- a/G0:G070/RTC/rtc.c
+++ b/G0:G070/RTC/rtc.c
@ -0,0 +1,61 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stm32g0.h>
+
+#include "rtc.h"
+
+#ifndef WAITWHILE
+#define WAITWHILE(x)  do{register uint32_t StartUpCounter = 0; while((x) && (++StartUpCounter < 0xffffff)){nop();}}while(0)
+#endif
+
+void rtc_setup(){
+    PWR->CR1 |= PWR_CR1_DBP; // disable RTC write protection
+    // turn on LSE and switch RTC to it
+    RCC->APBENR1 |= RCC_APBENR1_RTCAPBEN;
+    RCC->BDCR = RCC_BDCR_LSEON;
+    WAITWHILE(!(RCC->BDCR & RCC_BDCR_LSERDY));
+    RCC->BDCR |= RCC_BDCR_RTCEN | RCC_BDCR_RTCSEL_0;
+    // unlock RCC
+    RTC->WPR = 0xCA;
+    RTC->WPR = 0x53;
+    RTC->ICSR |= RTC_ICSR_INIT;
+    WAITWHILE(!(RTC->ICSR & RTC_ICSR_INITF));
+    RTC->PRER = (0x7f << RTC_PRER_PREDIV_A_Pos) | 0xff; // prediv_a = 127, prediv_s = 255
+    // here we can init starting time: monday of 1 jan 2001, 00:00:00
+//    RTC->DR = 1 << RTC_DR_YU_Pos | 1 << RTC_DR_WDU_Pos | 1 << RTC_DR_MU_Pos | 1 << RTC_DR_DU_Pos;
+//    RTC->TR = 0;
+    // RTC->CR is default - 0
+    // now turn off INIT bit, RTC will go on
+    RTC->ICSR &= ~RTC_ICSR_INIT;
+}
+
+void get_curtime(rtc_t *t){
+    WAITWHILE(!(RTC->ICSR & RTC_ICSR_RSF));
+    register uint32_t r = RTC->TR;
+    #define BCDu(shift)     ((r >> shift) & 0xf)
+    t->second = BCDu(RTC_TR_SU_Pos) + 10 * BCDu(RTC_TR_ST_Pos);
+    t->minute = BCDu(RTC_TR_MNU_Pos) + 10 * BCDu(RTC_TR_MNT_Pos);
+    t->hour = BCDu(RTC_TR_HU_Pos) + 10 * BCDu(RTC_TR_HT_Pos);
+    r = RTC->DR;
+    t->day = BCDu(RTC_DR_DU_Pos) + 10 * BCDu(RTC_DR_DT_Pos);
+    t->month = BCDu(RTC_DR_MU_Pos);
+    if(r & RTC_DR_MT) t->month += 10;
+    t->weekday = (r >> RTC_DR_WDU_Pos) & 0x7;
+    t->year = BCDu(RTC_DR_YU_Pos) + 10 * BCDu(RTC_DR_YT_Pos);
+}
--- a/G0:G070/RTC/rtc.cflags
+++ b/G0:G070/RTC/rtc.cflags
@ -0,0 +1 @@
+-std=c17
--- a/G0:G070/RTC/rtc.config
+++ b/G0:G070/RTC/rtc.config
@ -0,0 +1,3 @@
+#define EBUG
+#define STM32G0
+#define STM32G070xx
--- a/G0:G070/RTC/rtc.creator
+++ b/G0:G070/RTC/rtc.creator
@ -0,0 +1 @@
+[General]
--- a/G0:G070/RTC/rtc.creator.user
+++ b/G0:G070/RTC/rtc.creator.user
@ -0,0 +1,171 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE QtCreatorProject>
+<!-- Written by QtCreator 8.0.2, 2022-12-22T21:13:47. -->
+<qtcreator>
+ <data>
+  <variable>EnvironmentId</variable>
+  <value type="QByteArray">{7bd84e39-ca37-46d3-be9d-99ebea85bc0d}</value>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.ActiveTarget</variable>
+  <value type="int">0</value>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.EditorSettings</variable>
+  <valuemap type="QVariantMap">
+   <value type="bool" key="EditorConfiguration.AutoIndent">true</value>
+   <value type="bool" key="EditorConfiguration.AutoSpacesForTabs">false</value>
+   <value type="bool" key="EditorConfiguration.CamelCaseNavigation">true</value>
+   <valuemap type="QVariantMap" key="EditorConfiguration.CodeStyle.0">
+    <value type="QString" key="language">Cpp</value>
+    <valuemap type="QVariantMap" key="value">
+     <value type="QByteArray" key="CurrentPreferences">CppGlobal</value>
+    </valuemap>
+   </valuemap>
+   <valuemap type="QVariantMap" key="EditorConfiguration.CodeStyle.1">
+    <value type="QString" key="language">QmlJS</value>
+    <valuemap type="QVariantMap" key="value">
+     <value type="QByteArray" key="CurrentPreferences">QmlJSGlobal</value>
+    </valuemap>
+   </valuemap>
+   <value type="int" key="EditorConfiguration.CodeStyle.Count">2</value>
+   <value type="QByteArray" key="EditorConfiguration.Codec">KOI8-R</value>
+   <value type="bool" key="EditorConfiguration.ConstrainTooltips">false</value>
+   <value type="int" key="EditorConfiguration.IndentSize">4</value>
+   <value type="bool" key="EditorConfiguration.KeyboardTooltips">false</value>
+   <value type="int" key="EditorConfiguration.MarginColumn">80</value>
+   <value type="bool" key="EditorConfiguration.MouseHiding">true</value>
+   <value type="bool" key="EditorConfiguration.MouseNavigation">true</value>
+   <value type="int" key="EditorConfiguration.PaddingMode">1</value>
+   <value type="bool" key="EditorConfiguration.PreferSingleLineComments">false</value>
+   <value type="bool" key="EditorConfiguration.ScrollWheelZooming">true</value>
+   <value type="bool" key="EditorConfiguration.ShowMargin">false</value>
+   <value type="int" key="EditorConfiguration.SmartBackspaceBehavior">0</value>
+   <value type="bool" key="EditorConfiguration.SmartSelectionChanging">true</value>
+   <value type="bool" key="EditorConfiguration.SpacesForTabs">true</value>
+   <value type="int" key="EditorConfiguration.TabKeyBehavior">0</value>
+   <value type="int" key="EditorConfiguration.TabSize">8</value>
+   <value type="bool" key="EditorConfiguration.UseGlobal">true</value>
+   <value type="bool" key="EditorConfiguration.UseIndenter">false</value>
+   <value type="int" key="EditorConfiguration.Utf8BomBehavior">1</value>
+   <value type="bool" key="EditorConfiguration.addFinalNewLine">true</value>
+   <value type="bool" key="EditorConfiguration.cleanIndentation">false</value>
+   <value type="bool" key="EditorConfiguration.cleanWhitespace">true</value>
+   <value type="QString" key="EditorConfiguration.ignoreFileTypes">*.md, *.MD, Makefile</value>
+   <value type="bool" key="EditorConfiguration.inEntireDocument">false</value>
+   <value type="bool" key="EditorConfiguration.skipTrailingWhitespace">true</value>
+  </valuemap>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.PluginSettings</variable>
+  <valuemap type="QVariantMap">
+   <valuemap type="QVariantMap" key="AutoTest.ActiveFrameworks">
+    <value type="bool" key="AutoTest.Framework.Boost">true</value>
+    <value type="bool" key="AutoTest.Framework.CTest">false</value>
+    <value type="bool" key="AutoTest.Framework.Catch">true</value>
+    <value type="bool" key="AutoTest.Framework.GTest">true</value>
+    <value type="bool" key="AutoTest.Framework.QtQuickTest">true</value>
+    <value type="bool" key="AutoTest.Framework.QtTest">true</value>
+   </valuemap>
+   <valuemap type="QVariantMap" key="AutoTest.CheckStates"/>
+   <value type="int" key="AutoTest.RunAfterBuild">0</value>
+   <value type="bool" key="AutoTest.UseGlobal">true</value>
+   <valuemap type="QVariantMap" key="ClangTools">
+    <value type="bool" key="ClangTools.AnalyzeOpenFiles">true</value>
+    <value type="bool" key="ClangTools.BuildBeforeAnalysis">true</value>
+    <value type="QString" key="ClangTools.DiagnosticConfig">Builtin.DefaultTidyAndClazy</value>
+    <value type="int" key="ClangTools.ParallelJobs">2</value>
+    <valuelist type="QVariantList" key="ClangTools.SelectedDirs"/>
+    <valuelist type="QVariantList" key="ClangTools.SelectedFiles"/>
+    <valuelist type="QVariantList" key="ClangTools.SuppressedDiagnostics"/>
+    <value type="bool" key="ClangTools.UseGlobalSettings">true</value>
+   </valuemap>
+  </valuemap>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.Target.0</variable>
+  <valuemap type="QVariantMap">
+   <value type="QString" key="DeviceType">Desktop</value>
+   <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Desktop</value>
+   <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName">Desktop</value>
+   <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">{65a14f9e-e008-4c1b-89df-4eaa4774b6e3}</value>
+   <value type="int" key="ProjectExplorer.Target.ActiveBuildConfiguration">0</value>
+   <value type="int" key="ProjectExplorer.Target.ActiveDeployConfiguration">0</value>
+   <value type="int" key="ProjectExplorer.Target.ActiveRunConfiguration">0</value>
+   <valuemap type="QVariantMap" key="ProjectExplorer.Target.BuildConfiguration.0">
+    <value type="QString" key="ProjectExplorer.BuildConfiguration.BuildDirectory">/Big/Data/00__Electronics/STM32/G0-nolib/rtc</value>
+    <valuemap type="QVariantMap" key="ProjectExplorer.BuildConfiguration.BuildStepList.0">
+     <valuemap type="QVariantMap" key="ProjectExplorer.BuildStepList.Step.0">
+      <valuelist type="QVariantList" key="GenericProjectManager.GenericMakeStep.BuildTargets">
+       <value type="QString">all</value>
+      </valuelist>
+      <value type="bool" key="ProjectExplorer.BuildStep.Enabled">true</value>
+      <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">GenericProjectManager.GenericMakeStep</value>
+     </valuemap>
+     <value type="int" key="ProjectExplorer.BuildStepList.StepsCount">1</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Сборка</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName">Сборка</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.BuildSteps.Build</value>
+    </valuemap>
+    <valuemap type="QVariantMap" key="ProjectExplorer.BuildConfiguration.BuildStepList.1">
+     <valuemap type="QVariantMap" key="ProjectExplorer.BuildStepList.Step.0">
+      <valuelist type="QVariantList" key="GenericProjectManager.GenericMakeStep.BuildTargets">
+       <value type="QString">clean</value>
+      </valuelist>
+      <value type="bool" key="ProjectExplorer.BuildStep.Enabled">true</value>
+      <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">GenericProjectManager.GenericMakeStep</value>
+     </valuemap>
+     <value type="int" key="ProjectExplorer.BuildStepList.StepsCount">1</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Очистка</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName">Очистка</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.BuildSteps.Clean</value>
+    </valuemap>
+    <value type="int" key="ProjectExplorer.BuildConfiguration.BuildStepListCount">2</value>
+    <value type="bool" key="ProjectExplorer.BuildConfiguration.ClearSystemEnvironment">false</value>
+    <valuelist type="QVariantList" key="ProjectExplorer.BuildConfiguration.CustomParsers"/>
+    <value type="bool" key="ProjectExplorer.BuildConfiguration.ParseStandardOutput">false</value>
+    <valuelist type="QVariantList" key="ProjectExplorer.BuildConfiguration.UserEnvironmentChanges"/>
+    <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName">По умолчанию</value>
+    <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">GenericProjectManager.GenericBuildConfiguration</value>
+   </valuemap>
+   <value type="int" key="ProjectExplorer.Target.BuildConfigurationCount">1</value>
+   <valuemap type="QVariantMap" key="ProjectExplorer.Target.DeployConfiguration.0">
+    <valuemap type="QVariantMap" key="ProjectExplorer.BuildConfiguration.BuildStepList.0">
+     <value type="int" key="ProjectExplorer.BuildStepList.StepsCount">0</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DefaultDisplayName">Развёртывание</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.DisplayName">Развёртывание</value>
+     <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.BuildSteps.Deploy</value>
+    </valuemap>
+    <value type="int" key="ProjectExplorer.BuildConfiguration.BuildStepListCount">1</value>
+    <valuemap type="QVariantMap" key="ProjectExplorer.DeployConfiguration.CustomData"/>
+    <value type="bool" key="ProjectExplorer.DeployConfiguration.CustomDataEnabled">false</value>
+    <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.DefaultDeployConfiguration</value>
+   </valuemap>
+   <value type="int" key="ProjectExplorer.Target.DeployConfigurationCount">1</value>
+   <valuemap type="QVariantMap" key="ProjectExplorer.Target.RunConfiguration.0">
+    <valuelist type="QVariantList" key="CustomOutputParsers"/>
+    <value type="int" key="PE.EnvironmentAspect.Base">2</value>
+    <valuelist type="QVariantList" key="PE.EnvironmentAspect.Changes"/>
+    <value type="QString" key="ProjectExplorer.ProjectConfiguration.Id">ProjectExplorer.CustomExecutableRunConfiguration</value>
+    <value type="QString" key="ProjectExplorer.RunConfiguration.BuildKey"></value>
+    <value type="bool" key="RunConfiguration.UseCppDebugger">false</value>
+    <value type="bool" key="RunConfiguration.UseCppDebuggerAuto">true</value>
+    <value type="bool" key="RunConfiguration.UseQmlDebugger">false</value>
+    <value type="bool" key="RunConfiguration.UseQmlDebuggerAuto">true</value>
+   </valuemap>
+   <value type="int" key="ProjectExplorer.Target.RunConfigurationCount">1</value>
+  </valuemap>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.TargetCount</variable>
+  <value type="int">1</value>
+ </data>
+ <data>
+  <variable>ProjectExplorer.Project.Updater.FileVersion</variable>
+  <value type="int">22</value>
+ </data>
+ <data>
+  <variable>Version</variable>
+  <value type="int">22</value>
+ </data>
+</qtcreator>
--- a/G0:G070/RTC/rtc.cxxflags
+++ b/G0:G070/RTC/rtc.cxxflags
@ -0,0 +1 @@
+-std=c++17
--- a/G0:G070/RTC/rtc.files
+++ b/G0:G070/RTC/rtc.files
@ -0,0 +1,11 @@
+main.c
+rtc.c
+rtc.h
+usart.c
+usart.h
+strfunc.c
+strfunc.h
+proto.c
+proto.h
+i2c.c
+i2c.h
--- a/G0:G070/RTC/rtc.h
+++ b/G0:G070/RTC/rtc.h
@ -0,0 +1,36 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+// time, day of week (1 - monday), and date (1 - january)
+typedef struct{
+    uint8_t second;
+    uint8_t minute;
+    uint8_t hour;
+    uint8_t weekday;
+    uint8_t day;
+    uint8_t month;
+    uint8_t year;
+} rtc_t;
+
+void rtc_setup();
+
+void get_curtime(rtc_t *t);
--- a/G0:G070/RTC/rtc.includes
+++ b/G0:G070/RTC/rtc.includes
@ -0,0 +1,4 @@
+.
+../inc
+../inc/Fx
+../inc/cm
--- a/G0:G070/RTC/strfunc.c
+++ b/G0:G070/RTC/strfunc.c
@ -0,0 +1,255 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stm32g0.h>
+
+/**
+ * @brief hexdump - dump hex array by 16 bytes in string
+ * @param sendfun - function to send data
+ * @param arr - array to dump
+ * @param len - length of `arr`
+ */
+void hexdump(int (*sendfun)(const char *s), uint8_t *arr, uint16_t len){
+    char buf[52], *bptr = buf;
+    for(uint16_t l = 0; l < len; ++l, ++arr){
+        for(int16_t j = 1; j > -1; --j){
+            register uint8_t half = (*arr >> (4*j)) & 0x0f;
+            if(half < 10) *bptr++ = half + '0';
+            else *bptr++ = half - 10 + 'a';
+        }
+        if(l % 16 == 15){
+            *bptr++ = '\n';
+            *bptr = 0;
+            sendfun(buf);
+            bptr = buf;
+        }else *bptr++ = ' ';
+    }
+    if(bptr != buf){
+        *bptr++ = '\n';
+        *bptr = 0;
+        sendfun(buf);
+    }
+}
+
+/**
+ * @brief _2str - convert value into string buffer
+ * @param val - |value|
+ * @param minus - ==0 if value > 0
+ * @return buffer with number
+ */
+static char *_2str(uint32_t  val, uint8_t minus){
+    static char strbuf[12];
+    char *bufptr = &strbuf[11];
+    *bufptr = 0;
+    if(!val){
+        *(--bufptr) = '0';
+    }else{
+        while(val){
+            *(--bufptr) = val % 10 + '0';
+            val /= 10;
+        }
+    }
+    if(minus) *(--bufptr) = '-';
+    return bufptr;
+}
+
+// return string with number `val`
+char *u2str(uint32_t val){
+    return _2str(val, 0);
+}
+char *i2str(int32_t i){
+    uint8_t minus = 0;
+    uint32_t val;
+    if(i < 0){
+        minus = 1;
+        val = -i;
+    }else val = i;
+    return _2str(val, minus);
+}
+
+/**
+ * @brief uhex2str - print 32bit unsigned int as hex
+ * @param val - value
+ * @return string with number
+ */
+char *uhex2str(uint32_t val){
+    static char buf[12] = "0x";
+    int npos = 2;
+    uint8_t *ptr = (uint8_t*)&val + 3;
+    int8_t i, j, z=1;
+    for(i = 0; i < 4; ++i, --ptr){
+        if(*ptr == 0){ // omit leading zeros
+            if(i == 3) z = 0;
+            if(z) continue;
+        }
+        else z = 0;
+        for(j = 1; j > -1; --j){
+            uint8_t half = (*ptr >> (4*j)) & 0x0f;
+            if(half < 10) buf[npos++] = half + '0';
+            else buf[npos++] = half - 10 + 'a';
+        }
+    }
+    buf[npos] = 0;
+    return buf;
+}
+
+/**
+ * @brief omit_spaces - eliminate leading spaces and other trash in string
+ * @param buf - string
+ * @return - pointer to first character in `buf` > ' '
+ */
+char *omit_spaces(const char *buf){
+    while(*buf){
+        if(*buf > ' ') break;
+        ++buf;
+    }
+    return (char*)buf;
+}
+
+/**
+ * @brief getdec - read decimal number & return pointer to next non-number symbol
+ * @param buf - string
+ * @param N - number read
+ * @return Next non-number symbol. In case of overflow return `buf` and N==0xffffffff
+ */
+static char *getdec(const char *buf, uint32_t *N){
+    char *start = (char*)buf;
+    uint32_t num = 0;
+    while(*buf){
+        char c = *buf;
+        if(c < '0' || c > '9'){
+            break;
+        }
+        if(num > 429496729 || (num == 429496729 && c > '5')){ // overflow
+            *N = 0xffffff;
+            return start;
+        }
+        num *= 10;
+        num += c - '0';
+        ++buf;
+    }
+    *N = num;
+    return (char*)buf;
+}
+// read hexadecimal number (without 0x prefix!)
+static char *gethex(const char *buf, uint32_t *N){
+    char *start = (char*)buf;
+    uint32_t num = 0;
+    while(*buf){
+        char c = *buf;
+        uint8_t M = 0;
+        if(c >= '0' && c <= '9'){
+            M = '0';
+        }else if(c >= 'A' && c <= 'F'){
+            M = 'A' - 10;
+        }else if(c >= 'a' && c <= 'f'){
+            M = 'a' - 10;
+        }
+        if(M){
+            if(num & 0xf0000000){ // overflow
+                *N = 0xffffff;
+                return start;
+            }
+            num <<= 4;
+            num += c - M;
+        }else{
+            break;
+        }
+        ++buf;
+    }
+    *N = num;
+    return (char*)buf;
+}
+// read octal number (without 0 prefix!)
+static char *getoct(const char *buf, uint32_t *N){
+    char *start = (char*)buf;
+    uint32_t num = 0;
+    while(*buf){
+        char c = *buf;
+        if(c < '0' || c > '7'){
+            break;
+        }
+        if(num & 0xe0000000){ // overflow
+            *N = 0xffffff;
+            return start;
+        }
+        num <<= 3;
+        num += c - '0';
+        ++buf;
+    }
+    *N = num;
+    return (char*)buf;
+}
+// read binary number (without b prefix!)
+static char *getbin(const char *buf, uint32_t *N){
+    char *start = (char*)buf;
+    uint32_t num = 0;
+    while(*buf){
+        char c = *buf;
+        if(c < '0' || c > '1'){
+            break;
+        }
+        if(num & 0x80000000){ // overflow
+            *N = 0xffffff;
+            return start;
+        }
+        num <<= 1;
+        if(c == '1') num |= 1;
+        ++buf;
+    }
+    *N = num;
+    return (char*)buf;
+}
+
+/**
+ * @brief getnum - read uint32_t from string (dec, hex or bin: 127, 0x7f, 0b1111111)
+ * @param buf - buffer with number and so on
+ * @param N   - the number read
+ * @return pointer to first non-number symbol in buf
+ *      (if it is == buf, there's no number or if *N==0xffffffff there was overflow)
+ */
+char *getnum(const char *txt, uint32_t *N){
+    char *nxt = NULL;
+    char *s = omit_spaces(txt);
+    if(*s == '0'){ // hex, oct or 0
+        if(s[1] == 'x' || s[1] == 'X'){ // hex
+            nxt = gethex(s+2, N);
+            if(nxt == s+2) nxt = (char*)txt;
+        }else if(s[1] > '0'-1 && s[1] < '8'){ // oct
+            nxt = getoct(s+1, N);
+            if(nxt == s+1) nxt = (char*)txt;
+        }else{ // 0
+            nxt = s+1;
+            *N = 0;
+        }
+    }else if(*s == 'b' || *s == 'B'){
+        nxt = getbin(s+1, N);
+        if(nxt == s+1) nxt = (char*)txt;
+    }else{
+        nxt = getdec(s, N);
+        if(nxt == s) nxt = (char*)txt;
+    }
+    return nxt;
+}
+
+/*
+void mymemcpy(char *dest, const char *src, int len){
+    if(len < 1) return;
+    while(len--) *dest++ = *src++;
+}
+*/
--- a/G0:G070/RTC/strfunc.h
+++ b/G0:G070/RTC/strfunc.h
@ -0,0 +1,29 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <string.h>
+
+void hexdump(int (*sendfun)(const char *s), uint8_t *arr, uint16_t len);
+char *u2str(uint32_t val);
+char *i2str(int32_t i);
+char *uhex2str(uint32_t val);
+char *getnum(const char *txt, uint32_t *N);
+char *omit_spaces(const char *buf);
+//void mymemcpy(char *dest, const char *src, int len);
--- a/G0:G070/RTC/usart.c
+++ b/G0:G070/RTC/usart.c
@ -0,0 +1,177 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stm32g0.h>
+#include <string.h>
+
+#include "usart.h"
+
+// RX/TX DMA->CCR without EN flag
+#define DMARXCCR    (DMA_CCR_MINC | DMA_CCR_TCIE | DMA_CCR_TEIE)
+#define DMATXCCR    (DMA_CCR_MINC | DMA_CCR_DIR | DMA_CCR_TCIE | DMA_CCR_TEIE)
+
+volatile int u3txrdy = 1, u3rxrdy = 0; // transmission done, next line received
+static volatile int bufovr = 0, wasbufovr = 0; // Rx buffer overflow or error flag -> delete next line
+static volatile int rbufno = 0, tbufno = 0; // current buf number
+static volatile char rbuf[2][UARTBUFSZ], tbuf[2][UARTBUFSZ]; // receive & transmit buffers
+static volatile int rxlen[2] = {0}, txlen[2] = {0};
+
+char *usart3_getline(int *wasbo){
+    if(wasbo) *wasbo = wasbufovr;
+    wasbufovr = 0;
+    if(!u3rxrdy) return NULL;
+    u3rxrdy = 0; // clear ready flag
+    return (char*)rbuf[!rbufno]; // current buffer is in filling stage, return old - filled - buffer
+}
+
+#define USART_BRR(speed)    ((64000000 + speed/2) / speed)
+
+// USART3 @ PD8 (Tx) and PD9 (Rx) - both AF0
+void usart3_setup(){
+    RCC->IOPENR |= RCC_IOPENR_GPIODEN; // enable PD
+    RCC->AHBENR |= RCC_AHBENR_DMA1EN; // enable DMA1
+    // set PD8 and PD9 as AF
+    GPIOD->MODER = (GPIOD->MODER & ~(GPIO_MODER_MODE8 | GPIO_MODER_MODE9))
+            | GPIO_MODER_MODER8_AF | GPIO_MODER_MODER9_AF;
+    // AF0 for USART3 @ PD8/PD9
+    GPIOD->AFR[1] = GPIOD->AFR[1] & ~(GPIO_AFRH_AFSEL8 | GPIO_AFRH_AFSEL9);
+    // enable USART3 clocking
+    RCC->APBENR1 |= RCC_APBENR1_USART3EN;
+    // baudrate 115200
+    USART3->BRR = USART_BRR(115200);
+    // eol character: '/n'
+    USART3->CR2 = USART_CR2_ADD_VAL('\n');
+    // enable DMA transmission
+    USART3->CR3 = USART_CR3_DMAT | USART_CR3_DMAR;
+    // set up DMA channels: 2 - Tx, 3 - Rx
+    // Tx channel: mem++, mem->periph, 8bit, compl.&err. irq
+    DMA1_Channel2->CCR = DMATXCCR;
+    DMA1_Channel2->CPAR = (uint32_t) &USART3->TDR; // peripherial address
+    // Rx channel: mem++, periph->mem, 8bit, compl.&err. irq
+    DMA1_Channel3->CCR = DMARXCCR;
+    DMA1_Channel3->CPAR = (uint32_t) &USART3->RDR; // peripherial address
+    DMA1_Channel3->CNDTR = UARTBUFSZ;
+    DMA1_Channel3->CMAR = (uint32_t)&rbuf[rbufno];
+    // set up DMAMUX channels: 55 - USART3_TX, 54 - USART3_RX
+    // enumeration of DMAMUX starts from 0 (DMA - from 1)!
+    DMAMUX1_Channel1->CCR = 55;
+    DMAMUX1_Channel2->CCR = 54;
+    // charmatch interrupt, enable transmitter and receiver, enable usart
+    USART3->CR1 = USART_CR1_CMIE | USART_CR1_TE | USART_CR1_RE | USART_CR1_UE;
+    USART3->ICR = 0xffffffff; // clear all flags
+    DMA1_Channel3->CCR = DMARXCCR | DMA_CCR_EN; // start receiving right now
+    NVIC_EnableIRQ(USART3_4_IRQn);
+    NVIC_EnableIRQ(DMA1_Channel2_3_IRQn);
+}
+
+static int usart3_sendN(const char *str, int len){
+    int rest = UARTBUFSZ - txlen[tbufno];
+    if(rest == 0 && !u3txrdy) return 0; // buffer is full while transmission in process
+    if(len < rest) rest = len;
+    memcpy((char*)(tbuf[tbufno] + txlen[tbufno]), str, rest);
+    txlen[tbufno] += rest;
+    if(!u3txrdy) return rest;
+    if(txlen[tbufno] == UARTBUFSZ) usart3_sendbuf();
+    if(rest == len) return len;
+    len -= rest;
+    // now fill another - empty - buffer
+    if(len > UARTBUFSZ) len = UARTBUFSZ;
+    memcpy((char*)tbuf[tbufno], str + rest, len);
+    txlen[tbufno] = len;
+    return rest + len;
+}
+
+void usart3_send(const char *str, int len){
+    while(len){
+        int sent = usart3_sendN(str, len);
+        str += sent;
+        len -= sent;
+    }
+}
+
+void usart3_sendstr(const char *str){
+    int l = strlen(str);
+    usart3_send(str, l);
+}
+
+/**
+ * @brief usart3_sendbuf - send current buffer
+ */
+void usart3_sendbuf(){
+    if(!u3txrdy || txlen[tbufno] == 0) return;
+    // set up DMA
+    DMA1_Channel2->CCR = DMATXCCR;
+    DMA1_Channel2->CMAR = (uint32_t)&tbuf[tbufno];
+    DMA1_Channel2->CNDTR = txlen[tbufno];
+    USART3->ICR = USART_ICR_TCCF; // clear TC flag
+    u3txrdy = 0;
+    // activate DMA
+    DMA1_Channel2->CCR = DMATXCCR | DMA_CCR_EN;
+    tbufno = !tbufno; // swap buffers
+    txlen[tbufno] = 0;
+}
+
+// return amount of bytes sents
+int usart3_send_blocking(const char *str, int len){
+    if(!u3txrdy) return 0;
+    USART3->CR1 |= USART_CR1_TE;
+    for(int i = 0; i < len; ++i){
+        while(!(USART3->ISR & USART_ISR_TXE_TXFNF));
+        USART3->TDR = *str++;
+    }
+    return len;
+}
+
+// interrupt by '\n'
+void usart3_4_isr(){
+    if(USART3->ISR & USART_ISR_CMF){ // got '\n' @ USART3
+        DMA1_Channel3->CCR = DMARXCCR;
+        if(!bufovr){ // forget about broken line @ buffer overflow
+            u3rxrdy = 1;
+            int l = UARTBUFSZ - DMA1_Channel3->CNDTR - 1; // strlen
+            rxlen[rbufno] = l;
+            rbuf[rbufno][l] = 0;
+            rbufno = !rbufno;
+        }else{
+            bufovr = 0;
+            wasbufovr = 1;
+        }
+        // reload DMA Rx with next buffer
+        DMA1_Channel3->CMAR = (uint32_t)&rbuf[rbufno];
+        DMA1_Channel3->CNDTR = UARTBUFSZ;
+        DMA1_Channel3->CCR = DMARXCCR | DMA_CCR_EN;
+    }
+    USART3->ICR = 0xffffffff; // clear all flags
+}
+
+// ch2 - Tx, ch3 - Rx
+void dma1_channel2_3_isr(){
+    uint32_t isr = DMA1->ISR;
+    if(isr & (DMA_ISR_TCIF2 | DMA_ISR_TEIF2)){ // transfer complete or error
+        u3txrdy = 1;
+    }
+    if(isr & (DMA_ISR_TCIF3 | DMA_ISR_TEIF3)){ // receive complete or error -> buffer overflow
+        if(rbuf[rbufno][UARTBUFSZ-1] != '\n'){ // last symbol is not a newline
+            bufovr = 1;
+            DMA1_Channel3->CCR = DMARXCCR;
+            DMA1_Channel3->CNDTR = UARTBUFSZ;
+            DMA1_Channel3->CCR = DMARXCCR | DMA_CCR_EN;
+        }
+    }
+    DMA1->IFCR = 0xff0; // clear all flags for 2&3
+}
--- a/G0:G070/RTC/usart.h
+++ b/G0:G070/RTC/usart.h
@ -0,0 +1,32 @@
+/*
+ * This file is part of the rtc project.
+ * Copyright 2023 Edward V. Emelianov <edward.emelianoff@gmail.com>.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#define UARTBUFSZ   (64)
+
+#define USND(t)  do{usart3_sendstr(t);}while(0)
+
+extern volatile int u3txrdy, u3rxrdy;
+
+void usart3_setup();
+int usart3_send_blocking(const char *str, int len);
+void usart3_send(const char *str, int len);
+void usart3_sendbuf();
+char *usart3_getline(int *wasbo);
+void usart3_sendstr(const char *str);