Test USART reading

Makefile

@@ -8,6 +8,8 @@
 # GENERAL SETTINGS
 # ==============================================================================
 
+# NOTE: System clock frequency should be a multiple of 1.8432MHz for USART.
+
 SRCDIR    := src
 BINDIR    := bin
 TMPDIR    := $(BINDIR)/build
@@ -17,6 +19,7 @@ LOGFILE   := $(BINDIR)/core.log
 
 VERBOSE   := false
 ARCH      := m32
+#FREQ     := 7372800UL
 FREQ      := 8000000UL
 MCU       := atmega32a
 ASP       := usbasp

src/common.h

@@ -1,6 +1,7 @@
 #ifndef MAD_COMMON_H
 #define MAD_COMMON_H
 
+#define BIT(n)    (0x1U << (n))
 #define UNUSED(s) (void)(s)
 
 #include <stdlib.h>

src/main.c

@@ -1,5 +1,5 @@
 #include "common.h"
-#include "uart.h"
+#include "serial.h"
 
 #include <stdio.h>
 
@@ -17,17 +17,17 @@ int main(void)
 		return 1;
 	}
 
-	UART_Init();
+	USART_Init();
 
 	for (i = 1;; i++) {
 		if (i >= 99999) i = 1;
 
 		sprintf(buf, "[CORE] Fetching sensors #%05lu...\r\n", i);
-		UART_Write(buf);
+		USART_Write(buf);
 
-		UART_Read(&cmd, MAX_CMDBUF);
+		// USART_Read(&cmd, MAX_CMDBUF);
-		sprintf(buf, "[CORE] Checking cmdbuf=\"%s\"\r\n", cmd);
+		// sprintf(buf, "[CORE] Checking cmdbuf=\"%s\"\r\n", cmd);
-		UART_Write(buf);
+		// USART_Write(buf);
 
 		Sleep(3000);
 	}

src/serial.c

@@ -0,0 +1,76 @@
+#include "common.h"
+#include "serial.h"
+#include <avr/io.h>
+
+#include <stdio.h>
+
+#define USART_BAUDRATE 9600
+
+// Ensure closest fit for target baudrate
+//#define BAUD_PRESCALE (((F_CPU / (USART_BAUDRATE * 16UL))) - 1)
+#define BAUD_PRESCALE ((((F_CPU / 16) + (USART_BAUDRATE / 2)) \
+        / (USART_BAUDRATE)) - 1)
+
+static char USART_Rx(void);
+static void USART_Tx(char ch);
+
+void USART_Init(void)
+{
+	UCSRB |= BIT(RXEN) | BIT(TXEN); // Enable rx and tx circuitry
+	UCSRC |= BIT(URSEL) | BIT(UCSZ0) | BIT(UCSZ1); // 8-bit chars
+	UBRRH = (BAUD_PRESCALE >> 8); // Baud Rate upper byte
+	UBRRL = BAUD_PRESCALE; // Baud rate lower byte
+}
+
+void USART_Read(char **buf, int size)
+{
+	int n = 0;
+	char *p = *buf;
+	char ch;
+
+	if ((UCSRA & BIT(RXC)) == 0) {
+		p = '\0';
+		return;
+	}
+
+	do  {
+		// Discard messages exceeding
+		// given size limit quietly
+		if (n == size) {
+			p = '\0';
+			while (USART_Rx());
+			return;
+		}
+
+		ch = USART_Rx();
+		p[n] = ch;
+		n++;
+
+	} while (ch != '\0');
+}
+
+void USART_Write(const char *buf)
+{
+	int n = 0;
+
+	while (buf[n] != '\0') {
+		USART_Tx(buf[n++]);
+	}
+}
+
+static char USART_Rx(void)
+{
+	// Anything to read from UDR?
+	if ((UCSRA & BIT(RXC)) == 0)
+		return '\0';
+
+	return UDR;
+}
+
+static void USART_Tx(char ch)
+{
+	// Wait until UDR can receive data
+	while ((UCSRA & BIT(UDRE)) == 0);
+
+	UDR = ch;
+}

src/serial.h

@@ -0,0 +1,8 @@
+#ifndef MAD_SERIAL_H
+#define MAD_SERIAL_H
+
+void USART_Init(void);
+void USART_Read(char **buf, int size);
+void USART_Write(const char *buf);
+
+#endif // MAD_SERIAL_H

src/uart.c

@@ -1,67 +0,0 @@
-#include "common.h"
-#include <avr/io.h>
-
-#define BAUD_RATE 9600
-#define BAUD_PRESCALE (((F_CPU / (BAUD_RATE * 16UL))) - 1)
-
-static char UART_Rx(void);
-static void UART_Tx(char ch);
-
-void UART_Init(void)
-{
-        UCSRB |= (1 << RXEN) | (1 << TXEN);
-        UCSRC |= (1 << URSEL) | (1 << UCSZ0) | (1 << UCSZ1);
-        UBRRH = (BAUD_PRESCALE >> 8);
-        UBRRL = BAUD_PRESCALE;
-}
-
-
-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)
-{
-	int n = 0;
-
-	while (buf[n] != '\0') {
-		UART_Tx(buf[n++]);
-	}
-}
-
-static bool UART_IsReceiving(void)
-{
-	return ((UCSRA & (1 << RXC)) ? true : false);
-}
-
-static char UART_Rx(void)
-{
-	if (!UART_IsReceiving() || UDR == '\n')
-		return '\0';
-
-	return UDR;
-}
-
-static void UART_Tx(char ch)
-{
-	while ((UCSRA & (1 << UDRE)) == 0);
-	UDR = ch;
-}

src/uart.h

@@ -1,8 +0,0 @@
-#ifndef MAD_UART_H
-#define MAD_UART_H
-
-void UART_Init(void);
-void UART_Read(char **buf, int size);
-void UART_Write(const char *buf);
-
-#endif // MAD_UART_H