Implement basic UART reading

src/common.h

@@ -3,6 +3,8 @@
 
 #define UNUSED(s) (void)(s)
 
+#include <stdlib.h>
+#include <stdbool.h>
 #include <util/delay.h>
 #define Sleep(ms) _delay_ms(ms)
 

src/main.c

@@ -3,10 +3,19 @@
 
 #include <stdio.h>
 
+#define MAX_CMDBUF 256
+
 int main(void)
 {
 	unsigned long i;
 	char buf[128];
+	char *cmd;
+
+	// UART command buffer
+	cmd = malloc(MAX_CMDBUF);
+	if (cmd == NULL) {
+		return 1;
+	}
 
 	UART_Init();
 
@@ -16,6 +25,10 @@ int main(void)
 		sprintf(buf, "[CORE] Fetching sensors #%05lu...\r\n", i);
 		UART_Write(buf);
 
+		UART_Read(&cmd, MAX_CMDBUF);
+		sprintf(buf, "[CORE] Checking cmdbuf=\"%s\"\r\n", cmd);
+		UART_Write(buf);
+
 		Sleep(3000);
 	}
 

src/uart.c

@@ -15,14 +15,27 @@ void UART_Init(void)
         UBRRL = BAUD_PRESCALE;
 }
 
-void UART_Read(char **buf)
-{
-	// do {
-	//	p[n++] = UART_Rx();
-	// } while (p[n] != '\n');
 
-	UNUSED(UART_Rx);
-	UNUSED(buf);
+void UART_Read(char **buf, int size)
+{
+	int n = 0;
+	char *p = *buf;
+	char ch;
+
+	do  {
+		// Discard messages exceeding
+		// given size limit quietly
+		if (n == size) {
+			p = '\0';
+			while (UART_Rx());
+			return;
+		}
+
+		ch = UART_Rx();
+		p[n] = ch;
+		n++;
+
+	} while (ch != '\0');
 }
 
 void UART_Write(const char *buf)
@@ -34,9 +47,16 @@ void UART_Write(const char *buf)
 	}
 }
 
+static bool UART_IsReceiving(void)
+{
+	return ((UCSRA & (1 << RXC)) ? true : false);
+}
+
 static char UART_Rx(void)
 {
-	while ((UCSRA & (1 << RXC)) == 0);
+	if (!UART_IsReceiving() || UDR == '\n')
+		return '\0';
+
 	return UDR;
 }
 

src/uart.h

@@ -2,7 +2,7 @@
 #define MAD_UART_H
 
 void UART_Init(void);
-void UART_Read(char **buf);
+void UART_Read(char **buf, int size);
 void UART_Write(const char *buf);
 
 #endif // MAD_UART_H