changed to even parity in demo main function.

Makefile

@@ -8,7 +8,7 @@
 #MCU   = atmega2560
 #MCU   = attiny85
 MCU	= atmega328p
-F_CPU = 1000000UL
+F_CPU = 14745600UL
 BAUD  = 9600UL
 ## Also try BAUD = 19200 or 38400 if you're feeling lucky.
 
@@ -19,6 +19,10 @@ BAUD  = 9600UL
 #LIBDIR = /usr/lib/gcc/avr/5.4.0/
 LIBDIR = /lib/avr/
 
+#OUTPUT DIRs
+#This is to tell the makefile where we want to put the object and hex files etc
+DEBUG_DIR = ./out
+
 ##########------------------------------------------------------##########
 ##########                 Programmer Defaults                  ##########
 ##########          Set up once, then forget about it           ##########
@@ -57,7 +61,7 @@ TARGET = $(lastword $(subst /, ,$(CURDIR)))
 # Object files: will find all .c/.h files in current directory
 #  and in LIBDIR.  If you have any other (sub-)directories with code,
 #  you can add them in to SOURCES below in the wildcard statement.
-SOURCES=$(wildcard *.c $(LIBDIR)/*.c)
+SOURCES=$(wildcard src/*.c modules/*/*.c $(LIBDIR)/*.c)
 OBJECTS=$(SOURCES:.c=.o)
 HEADERS=$(SOURCES:.c=.h)
 
@@ -83,16 +87,16 @@ TARGET_ARCH = -mmcu=$(MCU)
 	 $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -o $@ $<;
 
 $(TARGET).elf: $(OBJECTS)
-	$(CC) $(LDFLAGS) $(TARGET_ARCH) $^ $(LDLIBS) -o $@
+	$(CC) $(LDFLAGS) $(TARGET_ARCH) $^ $(LDLIBS) -o $(DEBUG_DIR)/$@
 
 %.hex: %.elf
-	 $(OBJCOPY) -j .text -j .data -O ihex $< $@
+	 $(OBJCOPY) -j .text -j .data -O ihex $(DEBUG_DIR)/$< $(DEBUG_DIR)/$@
 
 %.eeprom: %.elf
-	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $< $@ 
+	$(OBJCOPY) -j .eeprom --change-section-lma .eeprom=0 -O ihex $(DEBUG_DIR)/$< $(DEBUG_DIR)/$@ 
 
 %.lst: %.elf
-	$(OBJDUMP) -S $< > $@
+	$(OBJDUMP) -S $(DEBUG_DIR)/$< > $(DEBUG_DIR)/$@
 
 ## These targets don't have files named after them
 .PHONY: all disassemble disasm eeprom size clean squeaky_clean flash fuses
@@ -131,7 +135,7 @@ squeaky_clean:
 ##########           Flashing code to AVR using avrdude         ##########
 ##########------------------------------------------------------##########
 
-flash: $(TARGET).hex 
+flash: $(DEBUG_DIR)/$(TARGET).hex 
 	$(AVRDUDE) -c $(PROGRAMMER_TYPE) -p $(MCU) $(PROGRAMMER_ARGS) -U flash:w:$<
 
 ## An alias
@@ -173,7 +177,7 @@ flash_109: flash
 #EFUSE=0x00 ##
 
 ## Mega 328p fuses
-LFUSE = 0x62
+LFUSE = 0x62	
 HFUSE = 0xd9
 EFUSE = 0xff
 
@@ -191,6 +195,14 @@ show_fuses:
 set_default_fuses:  FUSE_STRING = -U lfuse:w:$(LFUSE):m -U hfuse:w:$(HFUSE):m -U efuse:w:$(EFUSE):m 
 set_default_fuses:  fuses
 
+## For external clock low-power crystal.
+# The low order fuse is set for a low-power crystal. 14.7456Mhz
+# cksel[3:1] 8.0-16.0 = 111		//Sets it for the range of 8Mhz - 16Mhz
+# cksel[0] 1	SUT[1:0] 11		//gives 16K ck startup time aprox 65ms
+set_crystal_fuses: LFUSE = 0xFF
+set_crystal_fuses: FUSE_STRING = -U lfuse:w:$(LFUSE):m
+set_crystal_fuses: fuses
+
 ## Set the fuse byte for full-speed mode
 ## Note: can also be set in firmware for modern chips
 set_fast_fuse: LFUSE = 0xE2

README.md

@@ -9,6 +9,15 @@ Over time, I'm planning to add support for multiple AVR MCUs, however that
 may end up requiring more memory, so extensive of use of define macros will
 likely end up being the end result.
 
+Parity calculations are done in hardware automatically, so there are no
+functions written to interface with the serial error flags as the end user
+will know more about exception and error handling for their application.
+
+**2023-02-18:**
+Support for using external crystal oscillators was added to the makefile.
+Using a 14.7456Mhz crystal allows for reduced error rates when using
+any standard baud rates.
+
 
 ## Features:
 

src/avr_usart.c

@@ -1,7 +1,7 @@
 /*
  * Author: Jake Goodwin
  * Date: 2023
- * Description: Small library to communicate with the AT-09 bluetooth module. 
+ * Description: Small library to handle Serial communication on AVR micros 
  */
 
 #include <avr/io.h>
@@ -25,9 +25,8 @@ int main() {
 
     init_usart0(); 
 
-    //enable parity, because the internal 
-    //crystal is garbage
-    serial0_enable_parity_bit(2);
+    //enable even parity
+    serial0_enable_parity_bit(1);
 
     //enable interrupts
     sei();
@@ -64,8 +63,8 @@ int main() {
 void init_usart0(void) {
     //setup stuff for usart communications.
     
-    UBRR0H |= (uint8_t) (BT_UBRR>>8);
-    UBRR0L |= (uint8_t) BT_UBRR;
+    UBRR0H |= (uint8_t) (F_UBRR>>8);
+    UBRR0L |= (uint8_t) F_UBRR;
 
     //Enable recv and Transmit pins, overrides other uses.
     //IN the usart control and status register 0B
@@ -158,24 +157,6 @@ void serial0_write(unsigned char* buffer, uint8_t write_length) {
 
 }
 
-/*
- * Input: none
- * Output: none
- * Description:
- */
-void serial0_enable_line_feeds(void) {
-   ; 
-}
-
-/*
- * Input: none
- * Output: none
- * Description:
- */
-void serial0_enable_carriage_returns(void) {
-    ;
-}
-
 /*
  * Input: A parity setting as a 8bit uint
  * Output: none
@@ -233,40 +214,6 @@ void serial0_read(unsigned char* buffer, uint8_t buf_length) {
 }
 
 
-/*
- * Inupt: A serialbuffer and length
- * Output: None
- * Description: Reads the serial data into a buffer of x length, 
- * it does error checking from the register first.
- */
-void serial0_read_with_err_checking(unsigned char* buffer, uint8_t buf_length) {
-     //first wait for the data to be received.
-    while( !(UCSR0A & (1<<RXC0)) ) {
-        ;//Equiv of continue
-    }
-    
-    //check for errors in the register.
-    //Check for frame error.
-    if(UCSR0A & (1<<FE0)) {
-        led_blink();
-    }
-    //check for data over-run
-    else if(UCSR0A & (1<<DOR0)) {
-        led_blink();
-        led_blink();
-    }
-    //check for parity error
-    else if(UCSR0A & (1<<UPE0)) {
-        led_blink();
-        led_blink();
-        led_blink();
-    }
-
-    //now return the data
-    buffer[0] = UDR0;   
-}
-
-
 /*
  * Inupt: BUAD RATE as uint8_t
  * Output: None

src/avr_usart.h

@@ -4,7 +4,7 @@
  * Description: AT-09 Bluetooth module library for AVR micro crontrollers.
  * Filename: avr_at-09.h
  */
-#define __AVR_ATmega328P__
+//#define __AVR_ATmega328P__
 #include <inttypes.h>
 #include <stdint.h>
 
@@ -17,9 +17,18 @@
  * AVR D1 --> AT-09 RX
  * AVR D2 --> AT-09 State
  */
-#define FOSC        1000000UL
-#define BLE_BAUD    4800 
-#define BT_UBRR     ((FOSC)/(BLE_BAUD*16UL)-1)
+
+
+//F_CPU and BAUD should be defined with -D when compiling the code.
+#ifndef F_CPU
+    #define F_CPU   14745600UL
+#endif
+
+#ifndef BUAD
+    #define BAUD    4800 
+#endif
+
+#define F_UBRR     ((F_CPU)/(BAUD*16UL)-1)
 
 #define TX_PIN      PIND1
 #define TX_DDR      DDD1
@@ -55,12 +64,9 @@ unsigned char rx_usart0(void);
 
 void serial0_write(unsigned char* buffer, uint8_t write_length);
 void serial0_read(unsigned char* buffer, uint8_t buf_length);
-void serial0_read_with_err_checking(unsigned char* buffer, uint8_t buf_length);
 void serial0_set_baud(uint8_t baud);
 void seiral0_enable_timeouts(uint8_t ms);
 void serial0_flush_rxbuf(void);
-void serial0_enable_line_feeds(void);
-void serial0_enable_carriage_returns(void);
 void serial0_enable_parity_bit(uint8_t pos);
 void serial0_set_stop_bits(uint8_t number);