DS18B20 Sensor Detection via ONE-WIRE (1-Wire) Protocol

[Emanuele78]

Hi, where can I find a working One-Wire protocol? Is there an example provided by STM? I wrote code for a program to detect the temperature from a DS18B20 sensor, but I can’t detect the sensor, even though the debug shows everything is fine. Can someone help me? Thanks

[Emanuele78]

Hi, where can I find a working One-Wire protocol? Is there an example provided by STM? I wrote code for a program to detect the temperature from a DS18B20 sensor, but I can’t detect the sensor, even though the debug shows everything is fine. Can someone help me? Thanks

[Andrew Neil]

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@Emanuele78 wrote:

where can I find a working One-Wire protocol?

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From the manufacturer:

https://www.analog.com/en/resources/technical-articles/interfacing-the-ds18x20ds1822-1wire-temperature-sensor-in-a-microcontroller-environment.html

See also:

https://www.analog.com/en/resources/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html

Useful background info:

https://www.analog.com/en/resources/technical-articles/guidelines-for-reliable-long-line-1wire-networks.html

https://www.analog.com/en/resources/technical-articles/advanced-1-wire-network-driver.html

https://www.analog.com/en/resources/technical-articles/choosing-right-1-wire-master-for-embedded-applications.html

There are also UART-to-1-Wire and I2C-to-1-Wire hardware bridge chips.

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@Emanuele78 wrote:

 even though the debug shows everything is fine.  

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What "debug" is that?

Did you look at the 1-Wire line with an oscilloscope to see what was actually happening?

A useful feature of 1-Wire is that the timing between "Slots" (ie, bits) is non-critical - so you can step your code one complete Slot at a time ...

#1Wire

[Emanuele78]

Thanks, I will try to compare the links with my code.

Unfortunately, I don't have an oscilloscope, but if necessary, I will make sure to get one

I performed a debug with CUBEIDE using F6, placing breakpoints to check if the microcontroller detects the sensor, but it never finds it. The quantity variable in the following code is always zero.

/* Infinite loop */

/* USER CODE BEGIN WHILE */



while (1)

{

DS18B20_ReadAll();

HAL_GPIO_WritePin(Test_GPIO_Port, Test_Pin, 1);

DS18B20_StartAll();

HAL_GPIO_WritePin(Test_GPIO_Port, Test_Pin, 0);

uint8_t ROM_tmp[8];

uint8_t i;



int quantity = DS18B20_Quantity(); // quantity always = 0

[Andrew Neil]

Please see the Posting Tips for how to properly post source code:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

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@Emanuele78 wrote:

I performed a debug with CUBEIDE using F6, placing breakpoints to check if the microcontroller detects the sensor, but it never finds it. T= 0

---

Getting the correct timing on the wire is critical to 1-Wire operation - the CubeIDE debugger will not tell you anything about that.

It's also essential that your external hardware is correct - again, the CubeIDE debugger will not tell you anything about that.

This is why an oscilloscope is an essential tool for embedded firmware development: you need to be able to see what's happening in the real world of the hardware - not just the software.

https://community.st.com/t5/stm32-mcus-products/i-ran-printf-over-uart-but-the-results-were-not-displayed-in/m-p/723772/highlight/true#M261747

[Emanuele78]

Another question: if I run the program, it terminates after a few seconds. Can I understand through CUBEIDE why the program terminated? The only feedback I see is the attached image. Thanks again

[Emanuele78]

In reference to the external hardware, it seems to me that the connections are correct, as can be seen from the attached photos. Don't you think? Thanks

[Andrew Neil]

Please post a schematic

[Emanuele78]

Here it is.

Another question: if I run the program, it terminates after a few seconds. Can I understand through CUBEIDE why the program terminated? The only feedback I see is the attached image. Thanks again

[Emanuele78]

Measuring with a multimeter (See the code snippet I provide below.), the PROVA variable correctly changes state (from 3V to zero), while OneWire_OutputLow(onewire); gives me a value of only 2.1V from 3V (when it’s high), if I keep the external 4.7kOhm pull-up resistor connected.

If I remove the pull-up resistor, I get 2.8V high and 2.1V low.

Is the program able to detect the state change with this modest variability (3V high, 2.1V low)?

I would appreciate a response to the points mentioned above as well.

I'm using the code from https://github.com/lamik/DS18B20_STM32_HAL/blob/master/Src/onewire.c.

Thanks a lot

void OneWire_Init(OneWire_t* onewire, GPIO_TypeDef* GPIOx, uint16_t GPIO_Pin)
{
	HAL_TIM_Base_Start(&_DS18B20_TIMER); // Start the delay timer

	onewire->GPIOx = GPIOx; // Save 1-wire bus pin
	onewire->GPIO_Pin = GPIO_Pin;

	// 1-Wire bit bang initialization
	OneWire_BusOutputDirection(onewire);
	OneWire_OutputHigh(onewire);
	HAL_GPIO_WritePin(PROVA_GPIO_Port, PROVA_Pin, GPIO_PIN_SET);

	HAL_Delay(100);
	OneWire_OutputLow(onewire);
	HAL_GPIO_WritePin(PROVA_GPIO_Port, PROVA_Pin, GPIO_PIN_RESET);

	HAL_Delay(100);
	OneWire_OutputHigh(onewire);
	HAL_Delay(200);
}