Dallas iButton and UART

[SGian.1]

Hi there!

i start to work with Dallas Ibutton and for my project i use STM32G031K8 nucleo. Because i need to read only one ibutton i use the UART peripheral and no ic dedicate for 1Wire. My problem is when i try to  use the rx callback function for know when i receive all data (and i start wit  receive one bit at the time) never shoot, If i put a simple delay of 1ms everythingh wor very well i can see all my data on my logic analyzer .Question because the nucleo use the second uart2 for debug is possible that give me the problem ? and if yes how can i resolve ?

Thank you soo much 

Sergio

[TDK]

> Question because the nucleo use the second uart2 for debug is possible that give me the problem ?

No, if you're not using USART2 in your code, it won't affect your program. Doesn't matter that it's hooked up to the ST-Link chip.

 

[mƎALLEm]

Hello,

Not everyone here knows what "Dallas Ibutton" is. So, when you formulate a request please think about others that need the have a clear a picture of your issue/request.

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

 

[SGian.1]

Yep you have a reason 

https://www.analog.com/media/en/technical-documentation/data-sheets/DS1992-DS1993.pdf 

[Andrew Neil]

More specifically, you're talking about hacking 1-Wire^TM comms on a UART:

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

 

But, to understand what's going wrong with your implementation, you're going to have to give a lot more detail!

• Schematic of your connection
• Your code

See: 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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@SGian.1 wrote:

My problem is when i try to  use the rx callback function for know when i receive all data (and i start with  receive one bit at the time) never shoot

---

Before getting into 1-Wire^TM, have you got this working well on a "normal" serial connection to a terminal (or whatever)?

 

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@SGian.1 wrote:

If i put a simple delay of 1ms everything work very well i can see all my data on my logic analyzer

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So look carefully at your LA traces with & without that delay.

Compare & Contrast.

Does the non-working case comply with the 1-Wire^TM specifications?

As well as a LA, you should also check with an oscilloscope - that the analogue behaviour is correct ...

[Andrew Neil]

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@SGian.1 wrote:

If i put a simple delay of 1ms everything wor very well i can see all my data on my logic analyzer 

---

The AD article does say:

A delay may need to be added between the UART bytes being transmitted to allow for the required recovery time (T_REC)

https://www.analog.com/en/resources/technical-articles/using-a-uart-to-implement-a-1wire-bus-master.html#:~:text=A%20delay%20may%20need%20to%20be%20added%20between%20the%20UART%20bytes%20being%20transmitted%20to%20allow%20for%20the%20required%20recovery%20time%20(TREC)