TNE scooters controller via UART implementation

main.c

#include <avr/io.h>
#include <util/delay.h>
#include <avr/interrupt.h>
#include "uart.h"


// #define DEBUG (1)

uint8_t calcCRC();
static int analog_read();
long map(long x, long in_min, long in_max, long out_min, long out_max);

// int mmap(int x);

uint8_t buffer[20] = {1, 20, 1, 0, 0, 128, 0, 0, 0, 0, 0, 0, 0, 0, 0, 210, 0, 0, 5, 43}; //19 is CRC


int main(void)
{
	int speed  = 0;
	_delay_ms(500);
	int initSensor = analog_read();
	_delay_ms(300);

	DDRB &= ~_BV(PB4); // set data pin as INPUT


	while (1) {
		
		speed = map(analog_read(), initSensor, 850, 0, 5); // read analog value from sensor
		// speed = analog_read();
		// speed = mmap(analog_read());
	
		#ifndef DEBUG
		    buffer[16] = speed;
		    buffer[19] = calcCRC();
		    for(int i=0; i<20;i++) {
				uart_putc(buffer[i]);
		    }
		#endif  

		#ifdef DEBUG
			uart_putu(speed);
	   		uart_putc('\n');
		#endif  

		_delay_ms(28);
	}
}

uint8_t calcCRC() {
   uint8_t crc = 0;
   for (int i = 0; i < 19; i++) {
       crc ^= buffer[i];
   }
   return crc;
}


int analog_read()
{
	uint8_t low, high;

    ADMUX = _BV(MUX1); // ADC2

	ADMUX &= ~_BV(REFS0); // explicit set VCC as reference voltage (5V)
	ADCSRA |= _BV(ADEN);  // Enable ADC
	ADCSRA |= _BV(ADSC);  // Run single conversion
	while(bit_is_set(ADCSRA, ADSC)); // Wait conversion is done

	// Read values
	low = ADCL;
    high = ADCH;

    // combine the two bytes
    return (high << 8) | low;
}

long map(long x, long in_min, long in_max, long out_min, long out_max)
{
  return (x - in_min) * (out_max - out_min + 1) / (in_max - in_min + 1) + out_min;
}

// int mmap(int x) 
// {
// 	if(x <= 240) return 0U;
// 	if(x > 240 && x <= 380) return 1U;
// 	if(x > 380 && x <= 520) return 2U;
// 	if(x > 520 && x <= 660) return 3U;
// 	if(x > 660 && x <= 800) return 4U;
// 	if(x > 800) return 5U; else { return 0U; }
// }

Makefile

MCU=attiny13
FUSE_L=0x6A
FUSE_H=0xFF
F_CPU=1200000
CC=avr-gcc
LD=avr-ld
OBJCOPY=avr-objcopy
SIZE=avr-size
AVRDUDE=avrdude
CFLAGS=-std=c99 -Wall -g -Os -mmcu=${MCU} -DF_CPU=${F_CPU} -I. -I.. -DUART_RX_ENABLED -DUART_TX_ENABLED -DUART_BAUDRATE=19200
TARGET=main

SRCS=main.c uart.c

all:
	${CC} ${CFLAGS} -o ${TARGET}.o ${SRCS}
	${LD} -o ${TARGET}.elf ${TARGET}.o
	${OBJCOPY} -j .text -j .data -O ihex ${TARGET}.o ${TARGET}.hex
	${SIZE} -C --mcu=${MCU} ${TARGET}.elf
	${AVRDUDE} -p ${MCU} -c usbasp -U flash:w:${TARGET}.hex:i -F -P usb
	$(AVRDUDE) -p ${MCU} -c usbasp -U hfuse:w:${FUSE_H}:m -U lfuse:w:${FUSE_L}:m

build:
	${CC} ${CFLAGS} -o ${TARGET}.o ${SRCS}
	${LD} -o ${TARGET}.elf ${TARGET}.o
	${OBJCOPY} -j .text -j .data -O ihex ${TARGET}.o ${TARGET}.hex
	${SIZE} -C --mcu=${MCU} ${TARGET}.elf
	

flash:
	${AVRDUDE} -p ${MCU} -c usbasp -U flash:w:${TARGET}.hex:i -F -P usb

fuse:
	$(AVRDUDE) -p ${MCU} -c usbasp -U hfuse:w:${FUSE_H}:m -U lfuse:w:${FUSE_L}:m

clean:
	rm -f *.c~ *.o *.elf *.hex

uart.c

/**
 * Copyright (c) 2016, Łukasz Marcin Podkalicki <lpodkalicki@gmail.com>
 * Software UART for ATtiny13
 */

#include <avr/interrupt.h>
#include "uart.h"

void
uart_putc(char c)
{
	uint8_t sreg;

	sreg = SREG;
	cli();
	PORTB |= 1 << UART_TX;
	DDRB |= 1 << UART_TX;
	__asm volatile(
		" cbi %[uart_port], %[uart_pin] \n\t" // start bit
		" in r0, %[uart_port] \n\t"
		" ldi r30, 3 \n\t" // stop bit + idle state
		" ldi r28, %[txdelay] \n\t"
		"TxLoop: \n\t"
		// 8 cycle loop + delay - total = 7 + 3*r22
		" mov r29, r28 \n\t"
		"TxDelay: \n\t"
		// delay (3 cycle * delayCount) - 1
		" dec r29 \n\t"
		" brne TxDelay \n\t"
		" bst %[ch], 0 \n\t"
		" bld r0, %[uart_pin] \n\t"
		" lsr r30 \n\t"
		" ror %[ch] \n\t"
		" out %[uart_port], r0 \n\t"
		" brne TxLoop \n\t"
		:
		: [uart_port] "I" (_SFR_IO_ADDR(PORTB)),
		[uart_pin] "I" (UART_TX),
		[txdelay] "I" (TXDELAY),
		[ch] "r" (c)
		: "r0","r28","r29","r30"
	);
	SREG = sreg;
}

void uart_putu(uint16_t x)
{
        char buff[8] = {0};
        char *p = buff+6;
        do { *(p--) = (x % 10) + '0'; x /= 10; } while(x);
        uart_puts((const char *)(p+1));
}

void
uart_puts(const char *s)
{
     	while (*s) uart_putc(*(s++));
}

uart.h

/**
 * Copyright (c) 2016, Łukasz Marcin Podkalicki <lpodkalicki@gmail.com>
 * Software UART for ATtiny13
 */

#ifndef	_UART_H_
#define	_UART_H_

#ifndef F_CPU
# define        F_CPU           (1200000UL) // 1.2 MHz
#endif  /* !F_CPU */

# define        UART_TX         PB0 // Use PB0 as TX pin
# define        UART_BAUDRATE   (9600)

#define	TXDELAY         	(int)(((F_CPU/UART_BAUDRATE)-7 +1.5)/3)

void uart_putc(char c);
void uart_putu(uint16_t x);
void uart_puts(const char *s);

#endif	/* !_UART_H_ */