add usart over DMA Rx/Tx for G070

G0:G070/usart/main.c

@@ -0,0 +1,69 @@
+/*
+ * 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 "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();
+    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 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){
+            usart3_sendstr("\nI got: ");
+            usart3_sendstr(rcv);
+            usart3_send("\n\n", 2);
+        }
+    }
+}