/*
* DS18B20 input to port D4
* 8 digit 7-segment LED display with MAX7219 controller chip
* DIN <-> C6 (MOSI)
* CS <-> D2 (slave select)
* CLK <-> C5 (clock)
*/
#include <stdint.h>
#include "stm8.h"
/* 1-Wire (DS18B20 data) pin */
#define OW_PORT PA
#define OW_PIN PIN3
/* Simple busy loop delay */
void delay(unsigned long count) {
while (count--)
nop();
}
/* For LED-display */
void setup_spi() {
// SPI port setup: MISO is pullup in, MOSI & SCK are push-pull out
PC_DDR |= PIN5 | PIN6; // clock and MOSI
PC_CR1 |= PIN5 | PIN6 | PIN7;
// CS/SS (PD2) as output
PD_DDR |= PIN2;
PD_CR1 |= PIN2;
PD_ODR |= PIN2; // CS high
// SPI registers: First reset everything
SPI_CR1 = 0;
SPI_CR2 = 0;
// SPI_CR1 LSBFIRST=0 (MSB is transmitted first)
SPI_CR1 &= ~SPI_CR1_LSBFIRST;
// Baud Rate Control: 0b111 = fmaster / 256 (62,500 baud)
SPI_CR1 |= SPI_CR1_BR(0b111);
// SPI_CR1 CPOL=0 (Clock Phase, The first clock transition is the first data capture edge)
SPI_CR1 &= ~SPI_CR1_CPOL;
// SPI_CR1 CPHA=0 (Clock Polarity, SCK to 0 when idle)
SPI_CR1 &= ~SPI_CR1_CPHA;
SPI_CR2 |= SPI_CR2_SSM; // bit 1 SSM=1 Software slave management, enabled
SPI_CR2 |= SPI_CR2_SSI; // bit 0 SSI=1 Internal slave select, Master mode
SPI_CR1 |= SPI_CR1_MSTR; // CR1 bit 2 MSTR = 1, Master configuration.
}
uint8_t SPIOut(uint8_t data) {
SPI_CR1 |= SPI_CR1_MSTR;; // MSTR = 1, Master device.
SPI_CR1 |= SPI_CR1_SPE; // SPE, SPI Enable, Peripheral enabled
SPI_DR = data;
while (SPI_SR & SPI_SR_BSY); // SPI is busy in communication or Tx buffer is not empty
SPI_CR1 &= ~SPI_CR1_SPE; // Disable SPI
data = SPI_DR;
return data; // Not yet used.
}
void output_max(uint8_t address, uint8_t data) {
PD_ODR &= ~PIN2; // CS low
SPIOut(address);
SPIOut(data);
PD_ODR |= PIN2; // CS high
}
void init_max7219() {
uint8_t i;
output_max(0x0f, 0x00); //display test register - test mode off
output_max(0x0c, 0x01); //shutdown register - normal operation
output_max(0x0b, 0x07); //scan limit register - display digits 0 thru 7
output_max(0x0a, 0x01); //intensity register (1 = 3/32 on. 0xf is max)
output_max(0x09, 0xff); //decode mode register - CodeB decode all digits
// Blank all digits
for (i=1; i <= 8; i++) {
output_max(i, 0xf);
}
}
void display_number_dot(uint32_t number, uint8_t dot_pos, uint8_t is_negative) {
uint8_t pos=1;
if (number == 0)
output_max(pos++, 0);
while (number > 0 || dot_pos >= pos) {
uint8_t digit = number % 10;
if (pos == dot_pos) {
digit = digit | 0x80;
}
output_max(pos++, digit);
number /= 10;
}
if (is_negative) {
output_max(pos++, 0xa);
}
// clear rest of digits
while (pos <= 8) {
output_max(pos++, 0xf);
}
}
/********************** OneWire/DS18B20 routines ***************************/
void delay_us(uint16_t i) {
if (i < 9) { // FIXME: Really ugly
nop();
return;
}
TIM2_CNTRH = 0;
TIM2_CNTRL = 0;
TIM2_EGR = 0x01; // Update Generation
while(1) {
volatile uint16_t counter = (((TIM2_CNTRH) << 8) | TIM2_CNTRL);
if (i-6 < counter)
return;
}
}
#define OW_INPUT_MODE() PORT(OW_PORT,DDR) &= ~OW_PIN
#define OW_OUTPUT_MODE() PORT(OW_PORT,DDR) |= OW_PIN
#define OW_LOW() PORT(OW_PORT,ODR) &= ~OW_PIN
#define OW_HIGH() PORT(OW_PORT,ODR) |= OW_PIN
#define OW_READ() (PORT(OW_PORT,IDR) & OW_PIN)
void ow_pull_low(unsigned int us) {
OW_OUTPUT_MODE();
OW_LOW();
delay_us(us);
OW_INPUT_MODE();
}
void ow_write_byte(uint8_t out) {
uint8_t i;
for (i=0; i < 8; i++) {
if ( out & ((uint8_t)1<<i) ) {
// write 1
ow_pull_low(1);
delay_us(60);
} else {
// write 0
ow_pull_low(60);
delay_us(1);
}
}
}
uint8_t ow_read_byte() {
uint8_t val = 0;
uint8_t i;
for (i=0; i < 8; i++) {
ow_pull_low(1);
delay_us(5);
if (OW_READ()) {
val |= ((uint8_t)1<<i);
}
delay_us(55);
}
return val;
}
unsigned int ow_init() {
uint8_t input;
ow_pull_low(480);
delay_us(60);
input = !OW_READ();
delay_us(420);
return input;
}
unsigned int ow_convert_temperature() {
int cycles = 1; // For debugging purposes
ow_write_byte(0x44); // Convert Temperature
while (1) {
ow_pull_low(1);
delay_us(5);
if (OW_READ()) {
return cycles;
}
delay_us(55);
cycles++;
}
}
void display_ds_temperature(uint8_t high, uint8_t low) {
uint8_t is_negative = 0;
uint16_t decimals = 0; // 4 decimals (e.g. decimals 625 means 0.0625)
uint16_t i;
uint16_t temp = ((int16_t)high << 8) | low;
if (temp & 0x8000) {
is_negative = 1;
temp = (~temp) + 1;
}
low = temp & 0x0f;
temp = temp >> 4;
// low[3:0] mean values 0.5,0.25,0.125 and 0.0625
for (i=625; i <= 5000; i=i*2) {
if (low & 0x01) {
decimals += i;
}
low = low >> 1;
}
// Display temperature rounded to one decimal
display_number_dot((temp*1000 + ((decimals+5)/10) + 50)/100, 2, is_negative);
}
void read_ds18b20() {
uint8_t i;
uint8_t scratchpad[9];
if (ow_init()) {
ow_write_byte(0xcc); // Skip ROM
ow_convert_temperature();
ow_init();
ow_write_byte(0xcc); // Skip ROM
ow_write_byte(0xbe); // Read Scratchpad
for (i=0; i<9; i++) {
scratchpad[i] = ow_read_byte();
}
display_ds_temperature(scratchpad[1], scratchpad[0]);
} else {
/* DS18B20 was not detected */
output_max(0x8, 0xa);
}
}
/***************************************************************************/
int main(void)
{
/* Set clock to full speed (16 Mhz) */
CLK_CKDIVR = 0;
// Timer setup (for delay_us)
TIM2_PSCR = 0x4; // Prescaler: to 1MHz
TIM2_CR1 |= TIM_CR1_CEN; // Start timer
setup_spi();
init_max7219();
while(1) {
read_ds18b20();
delay(10000L);
}
}
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