add eeprom flash emulation for G0

2025-12-06 10:45:11 +03:00 · 2023-02-18 20:02:11 +03:00 · 2023-02-18 20:02:11 +03:00 · 87d9bc17c7
commit 87d9bc17c7
parent 2cc06884b4
18 changed files with 1155 additions and 0 deletions
--- a/G0:G070/flash/Makefile
+++ b/G0:G070/flash/Makefile
@ -0,0 +1,9 @@
+BINARY      := flash
+# MCU code
+MCU         := G070xx
+# change this linking script depending on particular MCU model,
+LDSCRIPT    := stm32g070xb.ld
+
+include ../makefile.g0
+include ../../makefile.stm32
+
--- a/G0:G070/flash/README
+++ b/G0:G070/flash/README
@ -0,0 +1,2 @@
+USART3 @ PD8/PD9 (115200, 8N1)
+EEPROM in Flash emulation
--- a/G0:G070/flash/flash.bin
+++ b/G0:G070/flash/flash.bin
--- a/G0:G070/flash/flash.c
+++ b/G0:G070/flash/flash.c
@ -0,0 +1,198 @@
+/*
+ * This file is part of the flash 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> // memcpy
+#include "flash.h"
+#include "strfunc.h"
+#include "usart.h"
+
+extern const uint32_t __varsstart, _BLOCKSIZE;
+
+static const uint32_t blocksize = (uint32_t)&_BLOCKSIZE;
+
+// max amount of Config records stored (will be recalculate in flashstorage_init()
+static uint32_t maxCnum = 1024 / sizeof(user_conf); // can't use blocksize here
+
+#define DEFMF   {.haveencoder = 1, .donthold = 1, .eswinv = 1, .keeppos = 1}
+
+#define USERCONF_INITIALIZER  {             \
+     .userconf_sz = sizeof(user_conf)       \
+    ,.flagU16 = 0xabcd                      \
+    ,.flagU32 = 0xdeadbeef                  \
+    ,.str = "test string"                   \
+    }
+
+static int erase_flash(const void*, const void*);
+static int write2flash(const void*, const void*, uint32_t);
+// don't write `static` here, or get error:
+//      'memcpy' forming offset 8 is out of the bounds [0, 4] of object '__varsstart' with type 'uint32_t'
+const user_conf *Flash_Data = (const user_conf *)(&__varsstart);
+
+user_conf the_conf = USERCONF_INITIALIZER;
+
+static int currentconfidx = -1; // index of current configuration
+
+/**
+ * @brief binarySearch - binary search in flash for last non-empty cell
+ *          any struct searched should have its sizeof() @ the first field!!!
+ * @param l - left index
+ * @param r - right index (should be @1 less than last index!)
+ * @param start - starting address
+ * @param stor_size - size of structure to search
+ * @return index of non-empty cell or -1
+ */
+static int binarySearch(int r, const uint8_t *start, int stor_size){
+    int l = 0;
+    while(r >= l){
+        int mid = l + (r - l) / 2;
+        const uint8_t *s = start + mid * stor_size;
+        if(*((const uint16_t*)s) == stor_size){
+            if(*((const uint16_t*)(s + stor_size)) == 0xffff){ // next is free
+                return mid;
+            }else{ // element is to the right
+                l = mid + 1;
+            }
+        }else{ // element is to the left
+            r = mid - 1;
+        }
+    }
+    return -1; // not found
+}
+
+/**
+ * @brief flashstorage_init - initialization of user conf storage
+ * run in once @ start
+ */
+void flashstorage_init(){
+    if(FLASH_SIZE > 0 && FLASH_SIZE < 20000){
+        uint32_t flsz = FLASH_SIZE * blocksize; // size in bytes
+        flsz -= (uint32_t)(&__varsstart) - FLASH_BASE;
+        maxCnum = flsz / sizeof(user_conf);
+    }
+    // -1 if there's no data at all & flash is clear; maxnum-1 if flash is full
+    currentconfidx = binarySearch((int)maxCnum-2, (const uint8_t*)Flash_Data, sizeof(user_conf));
+    if(currentconfidx > -1){
+        memcpy(&the_conf, &Flash_Data[currentconfidx], sizeof(user_conf));
+    }
+}
+
+// store new configuration
+// @return 0 if all OK
+int store_userconf(){
+    // maxnum - 3 means that there always should be at least one empty record after last data
+    // for binarySearch() checking that there's nothing more after it!
+    if(currentconfidx > (int)maxCnum - 3){ // there's no more place
+        currentconfidx = 0;
+        if(erase_flash(Flash_Data, NULL)) return 1;
+    }else ++currentconfidx; // take next data position (0 - within first run after firmware flashing)
+    return write2flash((const void*)&Flash_Data[currentconfidx], &the_conf, sizeof(the_conf));
+}
+
+static int write2flash(const void *start, const void *wrdata, uint32_t stor_size){
+    int ret = 0;
+    if (FLASH->CR & FLASH_CR_LOCK){ // unloch flash
+        FLASH->KEYR = FLASH_KEY1;
+        FLASH->KEYR = FLASH_KEY2;
+    }
+    // FLASH_SR_BSY2 for some
+    uint32_t count = (stor_size + 7) / 8;
+    volatile uint32_t *address = (volatile uint32_t*) start;
+    const uint32_t *data = (const uint32_t*) wrdata;
+    for(uint32_t i = 0; i < count; ++i){
+        while (FLASH->SR & (FLASH_SR_BSY1)); // 1: check BSY1
+        if(FLASH->SR & FLASH_SR_WRPERR){ // 2: check errors
+            return 1; // write protection
+        }
+        FLASH->SR = 0xffff; // clear all flags
+        FLASH->CR |= FLASH_CR_PG; // 3: set PG bit
+        IWDG->KR = IWDG_REFRESH;
+        *address++ = *data++; // 4: write both 32 bit words
+        *address++ = *data++;
+        while(FLASH->SR & FLASH_SR_BSY1);
+        if(FLASH->SR &  FLASH_SR_PGSERR){
+            ret = 1; // program error - meet not 0xffff
+            break;
+        }else{
+            for(int _ = 0; _ < 9999 && (!(FLASH->SR & FLASH_SR_EOP)); ++_);
+        }
+        FLASH->SR = 0xffff;
+    }
+    FLASH->CR &= ~(FLASH_CR_PG); // 7: clear PG bit at end of process
+    FLASH->CR |= FLASH_CR_LOCK; // lock it back
+    return ret;
+}
+
+/**
+ * @brief erase_flash - erase N pages of flash memory
+ * @param start  - first address
+ * @param end    - last address (or NULL if need to erase all flash remaining)
+ * @return 0 if succeed
+ */
+static int erase_flash(const void *start, const void *end){
+    int ret = 0;
+    if(!start) return 1;
+    uint32_t startb = (((uint32_t)start - FLASH_BASE) + blocksize - 1) / blocksize, endb;
+    if(!end){ // erase all remaining
+        endb = FLASH_SIZE / blocksize;
+    }else{ // erase a part
+        endb = (((uint32_t)end - FLASH_BASE) + blocksize - 1) / blocksize;
+    }
+    if ((FLASH->CR & FLASH_CR_LOCK) != 0){
+        FLASH->KEYR = FLASH_KEY1;
+        FLASH->KEYR = FLASH_KEY2;
+    }
+    for(uint32_t i = startb; i < endb; ++i){
+        IWDG->KR = IWDG_REFRESH;
+        /* (1) Wait till no operation is on going */
+        /* (2) Clear error & EOP bits */
+        while ((FLASH->SR & FLASH_SR_BSY1) != 0){} /* (1) */
+        FLASH->SR = 0xffff;  /* (2) */
+        /* (1) Set the PER bit in the FLASH_CR register to enable page erasing */
+        /* (2) Select the page to erase (PNB) */
+        /* (3) Set the STRT bit in the FLASH_CR register to start the erasing */
+        /* (4) Wait until BSY1 cleared */
+        FLASH->CR |= FLASH_CR_PER | i << FLASH_CR_PNB_Pos; /* (1) (2) */
+        FLASH->CR |= FLASH_CR_STRT; /* (3) */
+        while ((FLASH->SR & FLASH_SR_BSY1) != 0){} /* (4) */
+        FLASH->SR = FLASH_SR_EOP;
+        if(FLASH->SR & FLASH_SR_WRPERR){ /* Check Write protection error */
+            ret = 1;
+            FLASH->SR = FLASH_SR_WRPERR; /* Clear the flag by software by writing it at 1*/
+            break;
+        }
+        FLASH->CR &= ~FLASH_CR_PER; // clear PER
+    }
+    return ret;
+}
+
+void dump_userconf(){
+    SEND("flashsize="); printu(FLASH_SIZE);
+    SEND("\nuserconf_addr="); printuhex((uint32_t)Flash_Data);
+    SEND("\nuserconf_idx="); usart3_sendstr(i2str(currentconfidx));
+    SEND("\nuserconf_sz="); printu(the_conf.userconf_sz);
+    SEND("\nflagU16="); printuhex(the_conf.flagU16);
+    SEND("\nflagU32="); printuhex(the_conf.flagU32);
+    SEND("\nstr="); SEND(the_conf.str);
+    newline();
+    usart3_sendbuf();
+}
+
+int erase_storage(){
+    return erase_flash(Flash_Data, NULL);
+}
--- a/G0:G070/flash/flash.cflags
+++ b/G0:G070/flash/flash.cflags
@ -0,0 +1 @@
+-std=c17
--- a/G0:G070/flash/flash.config
+++ b/G0:G070/flash/flash.config
@ -0,0 +1,3 @@
+#define EBUG
+#define STM32G0
+#define STM32G070xx
--- a/G0:G070/flash/flash.creator
+++ b/G0:G070/flash/flash.creator
@ -0,0 +1 @@
+[General]
--- a/G0:G070/flash/flash.creator.user
+++ b/G0:G070/flash/flash.creator.user
@ -0,0 +1,171 @@
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--- a/G0:G070/flash/flash.cxxflags
+++ b/G0:G070/flash/flash.cxxflags
@ -0,0 +1 @@
+-std=c++17
--- a/G0:G070/flash/flash.files
+++ b/G0:G070/flash/flash.files
@ -0,0 +1,8 @@
+main.c
+usart.c
+
+flash.c
+flash.h
+strfunc.c
+strfunc.h
+usart.h
--- a/G0:G070/flash/flash.h
+++ b/G0:G070/flash/flash.h
@ -0,0 +1,38 @@
+/*
+ * This file is part of the flash 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
+
+/*
+ * struct to save user configurations
+ */
+typedef struct __attribute__((packed, aligned(8))){
+    uint16_t userconf_sz;           // "magick number"
+    uint16_t flagU16;
+    uint32_t flagU32;
+    char str[32];
+} user_conf;
+
+extern user_conf the_conf; // global user config (read from FLASH to RAM)
+// data from ld-file: start address of storage
+
+void flashstorage_init();
+int store_userconf();
+void dump_userconf();
+int erase_storage();
+
--- a/G0:G070/flash/flash.includes
+++ b/G0:G070/flash/flash.includes
@ -0,0 +1,4 @@
+.
+../inc
+../inc/Fx
+../inc/cm
--- a/G0:G070/flash/main.c
+++ b/G0:G070/flash/main.c
@ -0,0 +1,122 @@
+/*
+ * This file is part of the usart 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 "flash.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
+}
+
+static const char *helpmsg =
+        "'1' - change U16 value\n"
+        "'2' - change U32 value\n"
+        "'d' - dumpconf\n"
+        "'e' - erase flash\n"
+        "'f' - save conf to flash\n"
+        "'s' - change string (up to 31 symbol)\n"
+        "'t' - print Tms\n"
+;
+
+static void chstr(const char *s){
+    int i = 0;
+    for(; i < 31 && *s; ++i){
+        the_conf.str[i] = *s++;
+    }
+    the_conf.str[i] = 0;
+}
+
+int main(void){
+    StartHSE();
+    SysTick_Config(8000); // 1ms counter
+    flashstorage_init();
+    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 data over USART
+            if(!sent){
+                usart3_sendstr("Button pressed\n");
+                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){
+            char cmd = *rcv++;
+            uint32_t U, got = 0;
+            const char *n = getnum(rcv, &U);
+            if(n != rcv) got = 1;
+            switch(cmd){
+                case '1':
+                    if(!got || U > 0xffff) SEND("Need an uint16_t number\n");
+                    else the_conf.flagU16 = (uint16_t)U;
+                    SEND("Changed to "); printuhex(the_conf.flagU16); newline();
+                break;
+                case '2':
+                    if(!got) SEND("Need an uint32_t number\n");
+                    else the_conf.flagU32 = U;
+                    SEND("Changed to "); printuhex(the_conf.flagU32); newline();
+                break;
+                case 'd':
+                    dump_userconf();
+                break;
+                case 'e':
+                    if(erase_storage()) SEND("Error erasing\n");
+                    else SEND("Erased OK\n");
+                break;
+                case 'f':
+                    if(store_userconf()) SEND("Error: can't save\n");
+                    else SEND("OK, stored\n");
+                break;
+                case 's':
+                    chstr(omit_spaces(rcv));
+                    SEND("Changed to: "); SEND(the_conf.str); newline();
+                break;
+                case 't':
+                    SEND("Tms="); printu(Tms); newline();
+                break;
+                default: SEND(helpmsg);
+            }
+        }
+    }
+}
--- a/G0:G070/flash/openocd.cfg
+++ b/G0:G070/flash/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/flash/strfunc.c
+++ b/G0:G070/flash/strfunc.c
@ -0,0 +1,269 @@
+/*
+ * This file is part of the flash 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>
+
+/**
+ * @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){
+            uint32_t x = val / 10;
+            *(--bufptr) = (val - 10*x) + '0';
+            val = x;
+            //*(--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` > ' '
+ */
+const char *omit_spaces(const char *buf){
+    while(*buf){
+        if(*buf > ' ') break;
+        ++buf;
+    }
+    return 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 const 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 buf;
+}
+// read hexadecimal number (without 0x prefix!)
+static const char *gethex(const char *buf, uint32_t *N){
+    const char *start = 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 buf;
+}
+// read octal number (without 0 prefix!)
+static const char *getoct(const char *buf, uint32_t *N){
+    const 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 buf;
+}
+// read binary number (without b prefix!)
+static const char *getbin(const char *buf, uint32_t *N){
+    const 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 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)
+ */
+const char *getnum(const char *txt, uint32_t *N){
+    const char *nxt = NULL;
+    const 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;
+}
+
+// get signed integer
+const char *getint(const char *txt, int32_t *I){
+    const char *s = omit_spaces(txt);
+    int32_t sign = 1;
+    uint32_t U;
+    if(*s == '-'){
+    	sign = -1;
+    	++s;
+    }
+    const char *nxt = getnum(s, &U);
+    if(nxt == s) return txt;
+    if(U & 0x80000000) return txt; // overfull
+    *I = sign * (int32_t)U;
+    return nxt;
+}
+
--- a/G0:G070/flash/strfunc.h
+++ b/G0:G070/flash/strfunc.h
@ -0,0 +1,30 @@
+/*
+ * This file is part of the flash 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>
+#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);
+const char *getnum(const char *txt, uint32_t *N);
+const char *omit_spaces(const char *buf);
+const char *getint(const char *txt, int32_t *I);
--- a/G0:G070/flash/usart.c
+++ b/G0:G070/flash/usart.c
@ -0,0 +1,174 @@
+/*
+ * This file is part of the flash 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)
+
+static volatile int txrdy = 1, rxrdy = 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(!rxrdy) return NULL;
+    rxrdy = 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 void mymemcpy(char *dest, const char *src, int len){
+    while(len--) *dest++ = *src++;
+}
+
+int usart3_send(const char *str, int len){
+    int rest = UARTBUFSZ - txlen[tbufno];
+    if(rest == 0 && !txrdy) return 0; // buffer is full while transmission in process
+    if(len < rest) rest = len;
+    mymemcpy((char*)(tbuf[tbufno] + txlen[tbufno]), str, rest);
+    txlen[tbufno] += rest;
+    if(!txrdy) 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;
+    mymemcpy((char*)tbuf[tbufno], str + rest, len);
+    txlen[tbufno] = len;
+    return rest + len;
+}
+
+int usart3_sendstr(const char *str){
+    int l = strlen(str);
+    return usart3_send(str, l);
+}
+
+/**
+ * @brief usart3_sendbuf - send current buffer
+ */
+void usart3_sendbuf(){
+    if(!txrdy || 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
+    txrdy = 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(!txrdy) 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
+            rxrdy = 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
+        txrdy = 1;
+        //DMA1_Channel2->CCR = DMATXCCR;
+    }
+    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 = 0xffffffff; // clear all flags
+}
--- a/G0:G070/flash/usart.h
+++ b/G0:G070/flash/usart.h
@ -0,0 +1,35 @@
+/*
+ * This file is part of the flash 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 "strfunc.h"
+
+#define UARTBUFSZ   (512)
+
+#define SEND(x)     do{usart3_sendstr(x);}while(0)
+#define newline()   do{usart3_sendstr("\n");}while(0)
+#define printu(x)       do{usart3_sendstr(u2str(x));}while(0)
+#define printuhex(x)    do{usart3_sendstr(uhex2str(x));}while(0)
+
+void usart3_setup();
+int usart3_send_blocking(const char *str, int len);
+int usart3_send(const char *str, int len);
+void usart3_sendbuf();
+char *usart3_getline(int *wasbo);
+int usart3_sendstr(const char *str);