diff --git a/F303-nolib/Readme.md b/F303-nolib/Readme.md
new file mode 100644
index 0000000..7128e4d
--- /dev/null
+++ b/F303-nolib/Readme.md
@@ -0,0 +1,8 @@
+Samples for STM32F303 
+=================================
+
+Most of these samples works with [my non-solder devboard](https://github.com/eddyem/stm32samples/tree/master/F0_F1_F3-LQFP48_testboard)
+
+- blink - simple LEDs blink on PB0 and PB1
+- usart1 - read data from USART1 and send it back (blocking sending)
+- usarts - work with all three USARTs, send to USART1 data read from other, you can send "2\n" or "3\n" to USART1 for tests of USART2/USART3
diff --git a/F303-nolib/blink/blink.bin b/F303-nolib/blink/blink.bin
index 35409ea..45bc3be 100755
Binary files a/F303-nolib/blink/blink.bin and b/F303-nolib/blink/blink.bin differ
diff --git a/F303-nolib/inc/Fx/stm32f3.h b/F303-nolib/inc/Fx/stm32f3.h
index af491d3..1e6bc81 100644
--- a/F303-nolib/inc/Fx/stm32f3.h
+++ b/F303-nolib/inc/Fx/stm32f3.h
@@ -109,7 +109,7 @@ TRUE_INLINE int StartHSE(){ // system bus 72MHz from PLL
 #define WAITWHILE(x)  do{StartUpCounter = 0; while((x) && (++StartUpCounter < 0xffffff)){nop();}; if(x) return 0;}while(0)
     RCC->CR = (RCC->CR & ~RCC_CR_PLLON) | RCC_CR_HSEON; // disable PLL to reconfigure, enable HSE
     WAITWHILE(!(RCC->CR & RCC_CR_HSERDY));
-    // Enable Prefetch Buffer. Flash 2 wait states for 48..72MHz
+    // Enable Prefetch Buffer. Flash 4 wait states for 48..72MHz
     FLASH->ACR = (FLASH->ACR & ~(FLASH_ACR_LATENCY)) |
             FLASH_ACR_LATENCY_2 | FLASH_ACR_PRFTBE;
     // HCLK = SYSCLK (AHB prescaler = 1), PCLK1 = HCLK (APB1 prescaler = 1), PCLK2 = HCLK (APB2 prescaler = 1)
diff --git a/F303-nolib/inc/ld/stm32f3.ld b/F303-nolib/inc/ld/stm32f3.ld
index 56de5de..bffa48e 100644
--- a/F303-nolib/inc/ld/stm32f3.ld
+++ b/F303-nolib/inc/ld/stm32f3.ld
@@ -49,6 +49,10 @@ SECTIONS {
     _stext = .;
     *(.text*)
     *(.rodata*)
+    *(.glue_7)         /* glue arm to thumb code */
+    *(.glue_7t)        /* glue thumb to arm code */
+    KEEP (*(.init))
+    KEEP (*(.fini))
     . = ALIGN(4);
     _etext = .;
   } >rom
@@ -61,7 +65,7 @@ SECTIONS {
   .ARM : {
     *(.ARM.exidx*)
   } >rom
-  
+
   .data :
   {
     . = ALIGN(4);
@@ -74,11 +78,22 @@ SECTIONS {
   .myvars :
   {
     . = ALIGN(2048);
+    __varsstart = ABSOLUTE(.);
     KEEP(*(.myvars))
   } > rom
 
   _ldata = LOADADDR(.data);
 
+  .ccmram :
+  {
+    . = ALIGN(4);
+    _sccmram = .;
+    *(.ccmram)
+    *(.ccmram*)
+    . = ALIGN(4);
+    _eccmram = .;
+  } >ccmram AT> rom
+
   .bss :
   {
     . = ALIGN(4);
diff --git a/F303-nolib/usart1/Makefile b/F303-nolib/usart1/Makefile
new file mode 100644
index 0000000..7b02a34
--- /dev/null
+++ b/F303-nolib/usart1/Makefile
@@ -0,0 +1,146 @@
+BINARY		= usart1
+BOOTPORT	?= /dev/ttyUSB0
+BOOTSPEED	?= 115200
+# MCU FAMILY
+FAMILY		?= F3
+# MCU code
+MCU			?= F303xb
+# or __ARM_ARCH_7EM__
+ARMARCH = __ARM_ARCH_7M__
+# change this linking script depending on particular MCU model,
+LDSCRIPT	?= stm32f303xB.ld
+# debug
+#DEFS		= -DEBUG
+
+INDEPENDENT_HEADERS=
+
+FP_FLAGS	?= -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant
+ASM_FLAGS	?= -mthumb -mcpu=cortex-m4
+ARCH_FLAGS	= $(ASM_FLAGS) $(FP_FLAGS) -D $(ARMARCH)
+
+###############################################################################
+# Executables
+#PREFIX		?= arm-none-eabi
+# gcc from arm web site 
+PREFIX		?= /opt/bin/arm-none-eabi
+TOOLCHLIB	?= /opt/arm-none-eabi/lib
+RM			:= rm -f
+RMDIR		:= rmdir
+CC			:= $(PREFIX)-gcc
+# don't replace ld with gcc: the binary size would be much greater!!
+LD			:= $(PREFIX)-ld
+AR			:= $(PREFIX)-ar
+AS			:= $(PREFIX)-as
+SIZE 		:= $(PREFIX)-size
+OBJCOPY		:= $(PREFIX)-objcopy
+OBJDUMP		:= $(PREFIX)-objdump
+GDB			:= $(PREFIX)-gdb
+STFLASH		:= $(shell which st-flash)
+STBOOT		:= $(shell which stm32flash)
+DFUUTIL		:= $(shell which dfu-util)
+
+###############################################################################
+# Source files
+OBJDIR 		:= mk
+SRC			:= $(wildcard *.c)
+OBJS		:= $(addprefix $(OBJDIR)/, $(SRC:%.c=%.o))
+STARTUP		:= $(OBJDIR)/startup.o
+MAP			:= $(OBJDIR)/$(BINARY).map
+OBJS 		+= $(STARTUP)
+# dependencies: we need them to recompile files if their headers-dependencies changed
+DEPS		:= $(OBJS:.o=.d)
+
+INC_DIR ?= ../inc
+
+INCLUDE 	:= -I$(INC_DIR)/Fx -I$(INC_DIR)/cm
+LIB_DIR		:= $(INC_DIR)/ld
+
+###############################################################################
+# C flags
+CFLAGS		+= -g -gdwarf-2
+CFLAGS		+= -O2 -D__thumb2__=1 -MD
+CFLAGS		+= -Wall -Werror -Wextra -Wshadow 
+CFLAGS		+= -fshort-enums -ffunction-sections -fdata-sections
+#CFLAGS		+= -fno-common -ffunction-sections -fdata-sections -fno-stack-protector
+CFLAGS		+=  $(ARCH_FLAGS)
+
+###############################################################################
+# Linker flags
+#LDFLAGS		+= -nostartfiles --static -nostdlib  -specs=nosys.specs -specs=nano.specs
+LDFLAGS		+= $(ARCH_FLAGS)
+LDFLAGS		+= -specs=nosys.specs -specs=nano.specs
+LDFLAGS		+= -L$(LIB_DIR)
+#LDFLAGS		+= -L$(TOOLCHLIB)
+LDFLAGS		+= -T$(LDSCRIPT)
+LDFLAGS		+= -Wl,-Map=$(MAP),--cref -Wl,--gc-sections
+
+###############################################################################
+# Used libraries
+#LDLIBS		+=  -lc $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+
+DEFS		+= -DSTM32$(FAMILY) -DSTM32$(MCU)
+
+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) -o $@ -c $<
+
+$(OBJDIR)/%.o: %.c
+	@echo "  CC      $<"
+	$(CC) $(CFLAGS) $(DEFS) $(INCLUDE) -o $@ -c $<
+
+$(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)"
+	$(CC) $(LDFLAGS) $(OBJS) $(LDLIBS) -o $(ELF)
+
+size: $(ELF)
+	$(SIZE) $(ELF)    
+
+clean:
+	@echo "  CLEAN"
+	$(RM) $(OBJS) $(DEPS) $(ELF) $(HEX) $(LIST) $(MAP)
+	@rmdir $(OBJDIR) 2>/dev/null || true
+
+
+flash: $(BIN)
+	@echo "  FLASH  $(BIN)"
+	$(STFLASH) write $(BIN) 0x8000000
+
+boot: $(BIN)
+	@echo "  LOAD $(BIN) through bootloader"
+	$(STBOOT) -b$(BOOTSPEED) $(BOOTPORT) -w $(BIN)
+
+dfuboot: $(BIN)
+	@echo "  LOAD  $(BIN) THROUGH DFU"
+	$(DFUUTIL) -a0 -D $(BIN) -s 0x08000000
+
+.PHONY: clean flash boot
diff --git a/F303-nolib/usart1/hardware.c b/F303-nolib/usart1/hardware.c
new file mode 100644
index 0000000..2f09270
--- /dev/null
+++ b/F303-nolib/usart1/hardware.c
@@ -0,0 +1,32 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "hardware.h"
+#include "usart.h"
+
+static inline void gpio_setup(){
+    RCC->AHBENR |= RCC_AHBENR_GPIOAEN | RCC_AHBENR_GPIOBEN; // for USART and LEDs
+    for(int i = 0; i < 10000; ++i) nop();
+    GPIOB->MODER = GPIO_MODER_MODER0_O | GPIO_MODER_MODER1_O;
+    GPIOB->ODR = 1;
+}
+
+void hw_setup(){
+    gpio_setup();
+}
+
diff --git a/F303-nolib/usart1/hardware.h b/F303-nolib/usart1/hardware.h
new file mode 100644
index 0000000..b7ebcd6
--- /dev/null
+++ b/F303-nolib/usart1/hardware.h
@@ -0,0 +1,27 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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
+#ifndef __HARDWARE_H__
+#define __HARDWARE_H__
+
+#include "stm32f3.h"
+
+void hw_setup();
+
+#endif // __HARDWARE_H__
diff --git a/F303-nolib/usart1/main.c b/F303-nolib/usart1/main.c
new file mode 100644
index 0000000..a3af972
--- /dev/null
+++ b/F303-nolib/usart1/main.c
@@ -0,0 +1,52 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "stm32f3.h"
+#include "hardware.h"
+#include "usart.h"
+
+
+volatile uint32_t Tms = 0;
+
+void sys_tick_handler(void){
+    ++Tms;
+}
+
+int main(void){
+    if(!StartHSE()) StartHSI();
+    SysTick_Config((uint32_t)72000); // 1ms
+    hw_setup();
+    usart_setup();
+    uint32_t ctr = Tms;
+    while(1){
+        if(Tms - ctr > 499){
+            ctr = Tms;
+            pin_toggle(GPIOB, 1 << 1 | 1 << 0); // toggle LED @ PB0
+        }
+        if(bufovr){
+            bufovr = 0;
+            usart_send("bufovr\n");
+        }
+        char *txt = NULL;
+        if(usart_getline(&txt)){
+            usart_send("Get by USART1: ");
+            usart_send(txt);
+            usart_putchar('\n');
+        }
+    }
+}
diff --git a/F303-nolib/usart1/usart.c b/F303-nolib/usart1/usart.c
new file mode 100644
index 0000000..ee8fc03
--- /dev/null
+++ b/F303-nolib/usart1/usart.c
@@ -0,0 +1,106 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "stm32f3.h"
+#include "hardware.h"
+#include "usart.h"
+#include <string.h>
+
+static volatile int idatalen = 0; // received data line length (including '\n')
+
+volatile int linerdy = 0,   // received data ready
+    dlen    = 0,            // length of data (including '\n') in current buffer
+    bufovr  = 0;            // input buffer overfull
+
+static volatile int rbufno = 0; // current rbuf number
+static char rbuf[2][UARTBUFSZ]; // receive buffers
+static volatile char *recvdata = NULL;
+
+/**
+ * return length of received data (without trailing zero)
+ */
+int usart_getline(char **line){
+    if(bufovr){
+        bufovr = 0;
+        linerdy = 0;
+        return 0;
+    }
+    if(!linerdy) return 0;
+    *line = (char*)recvdata;
+    linerdy = 0;
+    return dlen;
+}
+
+void usart_putchar(const char ch){
+    while(!(USART1->ISR & USART_ISR_TXE));
+    USART1->TDR = ch;
+}
+void usart_sendn(const char *str, int L){
+    if(!str) return;
+    for(int i = 0; i < L; ++i){
+        usart_putchar(str[i]);
+    }
+}
+void usart_send(const char *str){
+    if(!str) return;
+    int L = 0;
+    const char *ptr = str;
+    while(*ptr++) ++L;
+    usart_sendn(str, L);
+}
+
+void usart_setup(){
+    // USART1: Rx - PA10 (AF7), Tx - PA9  (AF7)
+    // setup pins:
+    GPIOA->MODER = (GPIOA->MODER & ~(GPIO_MODER_MODER9 | GPIO_MODER_MODER10)) |
+                   GPIO_MODER_MODER9_AF | GPIO_MODER_MODER10_AF;
+    GPIOA->AFR[1] = (GPIOA->AFR[1] & ~(GPIO_AFRH_AFRH1 | GPIO_AFRH_AFRH2)) |
+                7 << (1 * 4) | 7 << (2 * 4); // PA9, PA10
+    // clock
+    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
+    USART1->ICR = 0xffffffff; // clear all flags
+    USART1->BRR = 720000 / 1152;
+    USART1->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE | USART_CR1_RXNEIE; // 1start,8data,nstop; enable Rx,Tx,USART
+    uint32_t tmout = 16000000;
+    while(!(USART1->ISR & USART_ISR_TC)){if(--tmout == 0) break;} // polling idle frame Transmission
+    USART1->ICR = 0xffffffff; // clear all flags again
+    NVIC_SetPriority(USART1_IRQn, 0);
+    NVIC_EnableIRQ(USART1_IRQn);
+}
+
+void usart1_exti25_isr(){
+    if(USART1->ISR & USART_ISR_RXNE){ // RX not emty - receive next char
+        // read RDR clears flag
+        uint8_t rb = USART1->RDR;
+        if(idatalen < UARTBUFSZ){ // put next char into buf
+            rbuf[rbufno][idatalen++] = rb;
+            if(rb == '\n'){ // got newline - line ready
+                linerdy = 1;
+                dlen = idatalen;
+                recvdata = rbuf[rbufno];
+                recvdata[dlen-1] = 0;
+                // prepare other buffer
+                rbufno = !rbufno;
+                idatalen = 0;
+            }
+        }else{ // buffer overrun
+            bufovr = 1;
+            idatalen = 0;
+        }
+    }
+}
diff --git a/F303-nolib/usart1/usart.h b/F303-nolib/usart1/usart.h
new file mode 100644
index 0000000..f252029
--- /dev/null
+++ b/F303-nolib/usart1/usart.h
@@ -0,0 +1,36 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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
+#ifndef __USART_H__
+#define __USART_H__
+
+#include "hardware.h"
+
+// input buffers size
+#define UARTBUFSZ  (80)
+
+extern volatile int linerdy, bufovr;
+
+void usart_setup();
+int usart_getline(char **line);
+void usart_send(const char *str);
+void usart_sendn(const char *str, int L);
+void usart_putchar(const char ch);
+
+#endif // __USART_H__
diff --git a/F303-nolib/usart1/usart1.bin b/F303-nolib/usart1/usart1.bin
new file mode 100755
index 0000000..b224843
Binary files /dev/null and b/F303-nolib/usart1/usart1.bin differ
diff --git a/F303-nolib/usarts/Makefile b/F303-nolib/usarts/Makefile
new file mode 100644
index 0000000..7ddce2f
--- /dev/null
+++ b/F303-nolib/usarts/Makefile
@@ -0,0 +1,146 @@
+BINARY		= usart
+BOOTPORT	?= /dev/ttyUSB0
+BOOTSPEED	?= 115200
+# MCU FAMILY
+FAMILY		?= F3
+# MCU code
+MCU			?= F303xb
+# or __ARM_ARCH_7EM__
+ARMARCH = __ARM_ARCH_7M__
+# change this linking script depending on particular MCU model,
+LDSCRIPT	?= stm32f303xB.ld
+# debug
+#DEFS		= -DEBUG
+
+INDEPENDENT_HEADERS=
+
+FP_FLAGS	?= -mfpu=fpv4-sp-d16 -mfloat-abi=hard -fsingle-precision-constant
+ASM_FLAGS	?= -mthumb -mcpu=cortex-m4
+ARCH_FLAGS	= $(ASM_FLAGS) $(FP_FLAGS) -D $(ARMARCH)
+
+###############################################################################
+# Executables
+#PREFIX		?= arm-none-eabi
+# gcc from arm web site 
+PREFIX		?= /opt/bin/arm-none-eabi
+TOOLCHLIB	?= /opt/arm-none-eabi/lib
+RM			:= rm -f
+RMDIR		:= rmdir
+CC			:= $(PREFIX)-gcc
+# don't replace ld with gcc: the binary size would be much greater!!
+LD			:= $(PREFIX)-ld
+AR			:= $(PREFIX)-ar
+AS			:= $(PREFIX)-as
+SIZE 		:= $(PREFIX)-size
+OBJCOPY		:= $(PREFIX)-objcopy
+OBJDUMP		:= $(PREFIX)-objdump
+GDB			:= $(PREFIX)-gdb
+STFLASH		:= $(shell which st-flash)
+STBOOT		:= $(shell which stm32flash)
+DFUUTIL		:= $(shell which dfu-util)
+
+###############################################################################
+# Source files
+OBJDIR 		:= mk
+SRC			:= $(wildcard *.c)
+OBJS		:= $(addprefix $(OBJDIR)/, $(SRC:%.c=%.o))
+STARTUP		:= $(OBJDIR)/startup.o
+MAP			:= $(OBJDIR)/$(BINARY).map
+OBJS 		+= $(STARTUP)
+# dependencies: we need them to recompile files if their headers-dependencies changed
+DEPS		:= $(OBJS:.o=.d)
+
+INC_DIR ?= ../inc
+
+INCLUDE 	:= -I$(INC_DIR)/Fx -I$(INC_DIR)/cm
+LIB_DIR		:= $(INC_DIR)/ld
+
+###############################################################################
+# C flags
+CFLAGS		+= -g -gdwarf-2
+CFLAGS		+= -O2 -D__thumb2__=1 -MD
+CFLAGS		+= -Wall -Werror -Wextra -Wshadow 
+CFLAGS		+= -fshort-enums -ffunction-sections -fdata-sections
+#CFLAGS		+= -fno-common -ffunction-sections -fdata-sections -fno-stack-protector
+CFLAGS		+=  $(ARCH_FLAGS)
+
+###############################################################################
+# Linker flags
+#LDFLAGS		+= -nostartfiles --static -nostdlib  -specs=nosys.specs -specs=nano.specs
+LDFLAGS		+= $(ARCH_FLAGS)
+LDFLAGS		+= -specs=nosys.specs -specs=nano.specs
+LDFLAGS		+= -L$(LIB_DIR)
+#LDFLAGS		+= -L$(TOOLCHLIB)
+LDFLAGS		+= -T$(LDSCRIPT)
+LDFLAGS		+= -Wl,-Map=$(MAP),--cref -Wl,--gc-sections
+
+###############################################################################
+# Used libraries
+#LDLIBS		+=  -lc $(shell $(CC) $(CFLAGS) -print-libgcc-file-name)
+
+DEFS		+= -DSTM32$(FAMILY) -DSTM32$(MCU)
+
+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) -o $@ -c $<
+
+$(OBJDIR)/%.o: %.c
+	@echo "  CC      $<"
+	$(CC) $(CFLAGS) $(DEFS) $(INCLUDE) -o $@ -c $<
+
+$(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)"
+	$(CC) $(LDFLAGS) $(OBJS) $(LDLIBS) -o $(ELF)
+
+size: $(ELF)
+	$(SIZE) $(ELF)    
+
+clean:
+	@echo "  CLEAN"
+	$(RM) $(OBJS) $(DEPS) $(ELF) $(HEX) $(LIST) $(MAP)
+	@rmdir $(OBJDIR) 2>/dev/null || true
+
+
+flash: $(BIN)
+	@echo "  FLASH  $(BIN)"
+	$(STFLASH) write $(BIN) 0x8000000
+
+boot: $(BIN)
+	@echo "  LOAD $(BIN) through bootloader"
+	$(STBOOT) -b$(BOOTSPEED) $(BOOTPORT) -w $(BIN)
+
+dfuboot: $(BIN)
+	@echo "  LOAD  $(BIN) THROUGH DFU"
+	$(DFUUTIL) -a0 -D $(BIN) -s 0x08000000
+
+.PHONY: clean flash boot
diff --git a/F303-nolib/usarts/hardware.c b/F303-nolib/usarts/hardware.c
new file mode 100644
index 0000000..3979f54
--- /dev/null
+++ b/F303-nolib/usarts/hardware.c
@@ -0,0 +1,32 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "hardware.h"
+#include "usart.h"
+
+static inline void gpio_setup(){
+    RCC->AHBENR |= RCC_AHBENR_GPIOAEN | RCC_AHBENR_GPIOBEN; // for USART and LEDs
+    for(int i = 0; i < 10; ++i) nop(); // don't know why, but next line won't work without a little delay
+    GPIOB->MODER = GPIO_MODER_MODER0_O | GPIO_MODER_MODER1_O;
+    GPIOB->ODR = 1;
+}
+
+void hw_setup(){
+    gpio_setup();
+}
+
diff --git a/F303-nolib/usarts/hardware.h b/F303-nolib/usarts/hardware.h
new file mode 100644
index 0000000..b7ebcd6
--- /dev/null
+++ b/F303-nolib/usarts/hardware.h
@@ -0,0 +1,27 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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
+#ifndef __HARDWARE_H__
+#define __HARDWARE_H__
+
+#include "stm32f3.h"
+
+void hw_setup();
+
+#endif // __HARDWARE_H__
diff --git a/F303-nolib/usarts/main.c b/F303-nolib/usarts/main.c
new file mode 100644
index 0000000..ef82493
--- /dev/null
+++ b/F303-nolib/usarts/main.c
@@ -0,0 +1,60 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "stm32f3.h"
+#include "hardware.h"
+#include "usart.h"
+
+
+volatile uint32_t Tms = 0;
+
+void sys_tick_handler(void){
+    ++Tms;
+}
+
+int main(void){
+    if(!StartHSE()) StartHSI();
+    SysTick_Config((uint32_t)72000); // 1ms
+    hw_setup();
+    usart_setup();
+    uint32_t ctr = Tms;
+    while(1){
+        if(Tms - ctr > 499){
+            ctr = Tms;
+            pin_toggle(GPIOB, 1 << 1 | 1 << 0); // toggle LED @ PB0
+           // usart_send(1, "test\n");
+           // transmit_tbuf();
+        }
+        for(int n = 1; n <= USARTNUM; ++n){
+            if(usartrx(n)){ // usart1 received data, store in in buffer
+                char *txt = NULL;
+                int r = usart_getline(n, &txt);
+                if(r){
+                    txt[r] = 0;
+                    usart_send(1, "Got by USART");
+                    char u[] = "0 : "; u[0] = '0' + n;
+                    usart_send(1, u);
+                    usart_send(1, txt);
+                    if(txt[0] == '2') usart_send(2, "Test for USART2\n");
+                    else if(txt[0] == '3') usart_send(3, "Test for USART3\n");
+                    transmit_tbuf();
+                }
+            }
+        }
+    }
+}
diff --git a/F303-nolib/usarts/usart.bin b/F303-nolib/usarts/usart.bin
new file mode 100755
index 0000000..88b01dd
Binary files /dev/null and b/F303-nolib/usarts/usart.bin differ
diff --git a/F303-nolib/usarts/usart.c b/F303-nolib/usarts/usart.c
new file mode 100644
index 0000000..8b15eba
--- /dev/null
+++ b/F303-nolib/usarts/usart.c
@@ -0,0 +1,242 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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 "stm32f3.h"
+#include "hardware.h"
+#include "usart.h"
+#include <string.h>
+
+extern volatile uint32_t Tms;
+// USART tx DMA 1: DMA1_Channel4, 2: DMA1_Channel7, 3: DMA1_Channel2
+static DMA_Channel_TypeDef *USARTDMA[USARTNUM] = {
+    DMA1_Channel4, DMA1_Channel7, DMA1_Channel2
+};
+static const uint32_t dmatcifs[USARTNUM] = {
+    DMA_ISR_TCIF4, DMA_ISR_TCIF7, DMA_ISR_TCIF2
+};
+static const uint32_t dmactcifs[USARTNUM] = {
+    DMA_IFCR_CTCIF4, DMA_IFCR_CTCIF7, DMA_IFCR_CTCIF2
+};
+static USART_TypeDef *USARTs[USARTNUM] = {
+    USART1, USART2, USART3
+};
+
+static volatile int idatalen[USARTNUM][2] = {0}; // received data line length (including '\n')
+static volatile int odatalen[USARTNUM][2] = {0};
+
+volatile int linerdy[USARTNUM] = {0}, // received data ready
+    dlen[USARTNUM] = {0},             // length of data (including '\n') in current buffer
+    bufovr[USARTNUM] = {0},           // input buffer overfull
+    txrdy[USARTNUM] = {1,1,1};        // transmission done
+
+
+int rbufno[USARTNUM] = {0}, tbufno[USARTNUM] = {0}; // current rbuf/tbuf numbers
+static char rbuf[USARTNUM][2][UARTBUFSZI], tbuf[USARTNUM][2][UARTBUFSZO]; // receive & transmit buffers
+static char *recvdata[USARTNUM] = {0};
+
+/**
+ * return length of received data (without trailing zero
+ * usartno: 1, 2 or 3
+ */
+int usart_getline(int usartno, char **line){
+    --usartno;
+    if(bufovr[usartno]){
+        bufovr[usartno] = 0;
+        linerdy[usartno] = 0;
+        return 0;
+    }
+    *line = recvdata[usartno];
+    linerdy[usartno] = 0;
+    return dlen[usartno];
+}
+
+// transmit current tbuf for all USARTs and swap buffers
+void transmit_tbuf(){
+    for(int usartno = 0; usartno < USARTNUM; ++usartno){
+        uint32_t p = 1000000;
+        while(!txrdy[usartno] && --p);
+        if(!txrdy[usartno]) continue;
+        register int l = odatalen[usartno][tbufno[usartno]];
+        if(!l) continue;
+        txrdy[usartno] = 0;
+        odatalen[usartno][tbufno[usartno]] = 0;
+        USARTDMA[usartno]->CCR &= ~DMA_CCR_EN;
+        USARTDMA[usartno]->CMAR = (uint32_t) tbuf[usartno][tbufno[usartno]]; // mem
+        USARTDMA[usartno]->CNDTR = l;
+        USARTDMA[usartno]->CCR |= DMA_CCR_EN;
+        tbufno[usartno] = !tbufno[usartno];
+    }
+}
+
+void usart_putchar(int usartno, const char ch){
+    --usartno;
+    if(odatalen[usartno][tbufno[usartno]] == UARTBUFSZO) transmit_tbuf();
+    tbuf[usartno][tbufno[usartno]][odatalen[usartno][tbufno[usartno]]++] = ch;
+}
+
+void usart_send(int usartno, const char *str){
+    --usartno;
+    while(*str){
+        if(odatalen[usartno][tbufno[usartno]] == UARTBUFSZO) transmit_tbuf();
+        tbuf[usartno][tbufno[usartno]][odatalen[usartno][tbufno[usartno]]++] = *str++;
+    }
+}
+
+void usart_sendn(int usartno, const char *str, uint32_t L){
+    --usartno;
+    for(uint32_t i = 0; i < L; ++i){
+        if(odatalen[usartno][tbufno[usartno]] == UARTBUFSZO) transmit_tbuf();
+        tbuf[usartno][tbufno[usartno]][odatalen[usartno][tbufno[usartno]]++] = *str++;
+    }
+}
+
+void newline(int usartno){
+    usart_putchar(usartno, '\n');
+    transmit_tbuf();
+}
+
+
+void usart_setup(){
+    // USART1: Rx - PA10 (AF7), Tx - PA9  (AF7)
+    // USART2: Rx - PA3 (AF7), Tx - PA2   (AF7)
+    // USART3: Rx - PB11 (AF7), Tx - PB10 (AF7)
+    // setup pins:
+    GPIOA->MODER = (GPIOA->MODER & ~(GPIO_MODER_MODER2|GPIO_MODER_MODER3|GPIO_MODER_MODER9 | GPIO_MODER_MODER10)) |
+                   GPIO_MODER_MODER2_AF | GPIO_MODER_MODER3_AF | GPIO_MODER_MODER9_AF | GPIO_MODER_MODER10_AF;
+    GPIOA->AFR[0] = (GPIOA->AFR[0] & ~(GPIO_AFRL_AFRL2 | GPIO_AFRL_AFRL3)) |
+                7 << (2 * 4) | 7 << (3 * 4); // PA2,3
+    GPIOA->AFR[1] = (GPIOA->AFR[1] & ~(GPIO_AFRH_AFRH1 | GPIO_AFRH_AFRH2)) |
+                7 << (1 * 4) | 7 << (2 * 4); // PA9, PA10
+    GPIOB->MODER = (GPIOB->MODER & ~(GPIO_MODER_MODER10 | GPIO_MODER_MODER11)) |
+                   GPIO_MODER_MODER10_AF | GPIO_MODER_MODER11_AF;
+    GPIOB->AFR[1] = (GPIOB->AFR[1] & ~(GPIO_AFRH_AFRH2 | GPIO_AFRH_AFRH3)) |
+            7 << (2 * 4) | 7 << (3 * 4); // PB10, PB11
+    // clock
+    RCC->APB2ENR |= RCC_APB2ENR_USART1EN;
+    RCC->APB1ENR |= RCC_APB1ENR_USART2EN;
+    RCC->APB1ENR |= RCC_APB1ENR_USART3EN;
+    RCC->AHBENR |= RCC_AHBENR_DMA1EN;
+    for(int i = 0; i < USARTNUM; ++i){
+        USARTs[i]->ICR = 0xffffffff; // clear all flags
+        // USARTX Tx DMA
+        USARTDMA[i]->CCR &= ~DMA_CCR_EN;
+        USARTDMA[i]->CPAR = (uint32_t) &USARTs[i]->TDR; // periph
+        USARTDMA[i]->CCR |= DMA_CCR_MINC | DMA_CCR_DIR | DMA_CCR_TCIE; // 8bit, mem++, mem->per, transcompl irq
+        // setup usarts
+        USARTs[i]->BRR = 720000 / 1152;
+        USARTs[i]->CR3 = USART_CR3_DMAT; // enable DMA Tx
+        USARTs[i]->CR1 = USART_CR1_TE | USART_CR1_RE | USART_CR1_UE | USART_CR1_RXNEIE; // 1start,8data,nstop; enable Rx,Tx,USART
+        uint32_t tmout = 16000000;
+        while(!(USARTs[i]->ISR & USART_ISR_TC)){if(--tmout == 0) break;} // polling idle frame Transmission
+        USARTs[i]->ICR = 0xffffffff; // clear all flags again
+    }
+    NVIC_SetPriority(DMA1_Channel2_IRQn, 3);
+    NVIC_EnableIRQ(DMA1_Channel2_IRQn);
+    NVIC_SetPriority(USART1_IRQn, 0);
+    NVIC_EnableIRQ(USART1_IRQn);
+    NVIC_SetPriority(DMA1_Channel4_IRQn, 3);
+    NVIC_EnableIRQ(DMA1_Channel4_IRQn);
+    NVIC_SetPriority(USART2_IRQn, 0);
+    NVIC_EnableIRQ(USART2_IRQn);
+    NVIC_SetPriority(DMA1_Channel7_IRQn, 3);
+    NVIC_EnableIRQ(DMA1_Channel7_IRQn);
+    NVIC_SetPriority(USART3_IRQn, 0);
+    NVIC_EnableIRQ(USART3_IRQn);
+}
+
+void usart_stop(){
+    RCC->APB2ENR &= ~RCC_APB2ENR_USART1EN;
+    RCC->APB1ENR &= ~RCC_APB1ENR_USART2EN;
+    RCC->APB1ENR &= ~RCC_APB1ENR_USART3EN;
+}
+
+static void usart_IRQ(int usartno){
+    USART_TypeDef *USARTX = USARTs[usartno];
+    //USND("USART"); USB_sendstr(u2str(usartno+1)); USND(" IRQ, ISR=");
+    //USB_sendstr(uhex2str(USARTX->ISR)); USND("\n");
+    #ifdef CHECK_TMOUT
+    static uint32_t tmout[USARTNUM] = {0};
+    #endif
+    if(USARTX->ISR & USART_ISR_RXNE){ // RX not emty - receive next char
+        #ifdef CHECK_TMOUT
+        if(tmout[usartno] && Tms >= tmout[usartno]){ // set overflow flag
+            bufovr[usartno] = 1;
+            idatalen[usartno][rbufno[usartno]] = 0;
+        }
+        tmout[usartno] = Tms + TIMEOUT_MS;
+        if(!tmout[usartno]) tmout[usartno] = 1; // prevent 0
+        #endif
+        // read RDR clears flag
+        uint8_t rb = USARTX->RDR;
+        //USND("RB="); USB_sendstr(uhex2str(rb)); USND("\n");
+        if(idatalen[usartno][rbufno[usartno]] < UARTBUFSZI){ // put next char into buf
+            rbuf[usartno][rbufno[usartno]][idatalen[usartno][rbufno[usartno]]++] = rb;
+            if(rb == '\n'){ // got newline - line ready
+                //USND("Newline\n");
+                linerdy[usartno] = 1;
+                dlen[usartno] = idatalen[usartno][rbufno[usartno]];
+                recvdata[usartno] = rbuf[usartno][rbufno[usartno]];
+                // prepare other buffer
+                rbufno[usartno] = !rbufno[usartno];
+                idatalen[usartno][rbufno[usartno]] = 0;
+                #ifdef CHECK_TMOUT
+                // clear timeout at line end
+                tmout[usartno] = 0;
+                #endif
+            }
+        }else{ // buffer overrun
+            bufovr[usartno] = 1;
+            idatalen[usartno][rbufno[usartno]] = 0;
+            #ifdef CHECK_TMOUT
+            tmout[usartno] = 0;
+            #endif
+        }
+    }
+}
+
+static void usart_dma_IRQ(int usartno){
+    if(DMA1->ISR & dmatcifs[usartno]){
+        DMA1->IFCR |= dmactcifs[usartno];
+        txrdy[usartno] = 1;
+    }
+}
+
+// USART1 Rx
+void usart1_exti25_isr(){
+    usart_IRQ(0);
+}
+// USART2 Rx
+void usart2_exti26_isr(){
+    usart_IRQ(1);
+}
+// USART3 Rx
+void usart3_exti28_isr(){
+    usart_IRQ(2);
+}
+// USART1 Tx
+void dma1_channel4_isr(){
+    usart_dma_IRQ(0);
+}
+// USART2 Tx
+void dma1_channel7_isr(){
+    usart_dma_IRQ(1);
+}
+// USART3 Tx
+void dma1_channel2_isr(){
+    usart_dma_IRQ(2);
+}
diff --git a/F303-nolib/usarts/usart.h b/F303-nolib/usarts/usart.h
new file mode 100644
index 0000000..f6a4f7c
--- /dev/null
+++ b/F303-nolib/usarts/usart.h
@@ -0,0 +1,52 @@
+/*
+ * This file is part of the F303usart project.
+ * Copyright 2021 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
+#ifndef __USART_H__
+#define __USART_H__
+
+#include "hardware.h"
+
+#define USARTNUM    (3)
+
+// input and output buffers size
+#define UARTBUFSZI  (80)
+#define UARTBUFSZO  (80)
+// timeout between data bytes
+#ifndef TIMEOUT_MS
+#define TIMEOUT_MS (1500)
+#endif
+
+// macro for static strings
+#define SEND(n, str) usart_send(n, str)
+
+#define usartrx(n)  (linerdy[n-1])
+#define usartovr(n) (bufovr[n-1])
+
+extern volatile int linerdy[], bufovr[], txrdy[];
+
+void transmit_tbuf();
+void usart_setup();
+int usart_getline(int usartno, char **line);
+void usart_send(int usartno, const char *str);
+void usart_sendn(int usartno, const char *str, uint32_t L);
+void newline(int usartno);
+void usart_putchar(int usartno, const char ch);
+void usart_stop();
+
+#endif // __USART_H__