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Hi. I'm using STM32F030C8T6 MCU to communicate with multiple DS18B20. I'm using Timers to make 1us delay. I set my prescaler to 48-1. and I'm running on 48MHz clock. when i connect two sensors to my MCU, i can't read temperature, so for testing i disconnected one of the sensors and connect only one sensor to MCU. when i run skip command and convert temperature and read scratchpad its ok. so i decided to instead of ROM skip command use ROM match command to see what happened. when i use Search command thee output is always 255 or 0xff. i think timing is correct because 0xCC and 0xBE and reading data is ok. here is the code:
C:
void delay (ds18Config* _ds18b20, uint16_t time)
{
/* change your code here for the delay in microseconds */
//test = HAL_GetTick();
__HAL_TIM_SET_COUNTER(_ds18b20->hTIMx, 0);
while ((__HAL_TIM_GET_COUNTER(_ds18b20->hTIMx))<time);
}
void DS18B20_Write_Command (ds18Config* _ds18b20, uint8_t data)
{
uint8_t bitMask;
Set_Pin_Output(_ds18b20->sensorPort, _ds18b20->sensorPin); // set as output
for (bitMask = 0x01; bitMask; bitMask <<= 1){
if ((data & bitMask)!=0){
Set_Pin_Output(_ds18b20->sensorPort, _ds18b20->sensorPin); // set as output
HAL_GPIO_WritePin (_ds18b20->sensorPort, _ds18b20->sensorPin, 0); // pull the pin LOW
delay (_ds18b20, 10); // wait for 1 us
Set_Pin_Input(_ds18b20->sensorPort, _ds18b20->sensorPin); // set as input
delay (_ds18b20, 55); // wait for 60 us
}else{
Set_Pin_Output(_ds18b20->sensorPort, _ds18b20->sensorPin);
HAL_GPIO_WritePin (_ds18b20->sensorPort, _ds18b20->sensorPin, 0); // pull the pin LOW
delay (_ds18b20, 65); // wait for 60 us
Set_Pin_Input(_ds18b20->sensorPort, _ds18b20->sensorPin);
delay (_ds18b20, 5);
}
}
}
uint8_t DS18B20_Read (ds18Config* _ds18b20)
{
uint8_t value=0;
Set_Pin_Input(_ds18b20->sensorPort, _ds18b20->sensorPin);
for (int i=0;i<8;i++){
Set_Pin_Output(_ds18b20->sensorPort, _ds18b20->sensorPin); // set as output
HAL_GPIO_WritePin (_ds18b20->sensorPort, _ds18b20->sensorPin, 0); // pull the data pin LOW
delay (_ds18b20, 3); // wait for > 1us
Set_Pin_Input(_ds18b20->sensorPort, _ds18b20->sensorPin); // set as input
if (HAL_GPIO_ReadPin (_ds18b20->sensorPort, _ds18b20->sensorPin)){
value |= 1<<i; // read = 1
}
delay (_ds18b20, 53); // wait for 60 us
}
return value;
}
void DS18B20_getTemperature(ds18Config *_ds18b20, ds18Data *_sensors) {
uint8_t Temp_byte1, Temp_byte2;
uint16_t TEMP;
uint8_t data[1];
uint8_t address0[8] = {0x28, 0xFF, 0x64, 0x1E, 0x85, 0xF5, 0xFD, 0xD3};
DS18B20_Start(_ds18b20);
HAL_Delay (1);
DS18B20_Write_Command (_ds18b20, 0xcc); // skip ROM
DS18B20_Write_Command (_ds18b20, 0x44); // convert t
HAL_Delay (800);
DS18B20_Start(_ds18b20);
HAL_Delay (1);
DS18B20_Write_Command (_ds18b20, 0x55);
for (int i = 0; i <8; i++){
DS18B20_Write_Command (_ds18b20, address0[i]);
}
DS18B20_Write_Command (_ds18b20, 0xBE);
Temp_byte1 = DS18B20_Read(_ds18b20);
Temp_byte2 = DS18B20_Read(_ds18b20);
TEMP = (Temp_byte2<<8)|Temp_byte1;
data[0] = (int)TEMP/16;
}
