Best approach to interface HX711 with Nordic nrf52832?

RE: Best approach to interface HX711 with Nordic nrf52832?

nrf_user — Wed, 19 Jun 2024 23:20:28 GMT

I have a separate solution to this problem that's preferable in a few ways:

Only one timer instance is needed, instead of 2
The processing is done in interrupts, so you don't need to wait while polling
There are no more corrupt samples

The main realization behind it is that the hx711 will shut down if the clock line is held high for too long. When a high priority interrupt (from soft device, for example) arrives it can cause a delay which leaves the clock high and causes the hx711 to shut down. What my solution does is to use a timer / PPI to turn the clock on, then off, then calls an interrupt which can read the data and resume the timer. If an interrupt arrives and adds latency, this extra time occurs with the clock low, which is allowed for arbitrary lengths of time.

You can find the code: here

Suggestions for improvements are always welcome!

RE: Best approach to interface HX711 with Nordic nrf52832?

Sandy.ashva — Mon, 07 Sep 2020 11:39:50 GMT

What optimizations have to be turned on?

RE: Best approach to interface HX711 with Nordic nrf52832?

Germàn — Sat, 23 Feb 2019 18:37:57 GMT

Good afternoon. I am totally new to programming with controllers ARM Cortex M-4 and I need to do to operate the ADC HX711 in a Nrf52DK without the use of Ble. I have searched to the best of examples for the forums and I have not solved my needs. I can only find examples of Main c. for use with Ble. Someone could help me to build the file Main c. to be able to read the HX711 through NRF_LOG_INFO? I appreciate deeply the help.

RE: Best approach to interface HX711 with Nordic nrf52832?

awneil — Fri, 21 Dec 2018 14:50:22 GMT

Again: use the debugger to step through your code and see where, exactly, it is getting stuck!

RE: Best approach to interface HX711 with Nordic nrf52832?

faizi_968 — Fri, 21 Dec 2018 12:13:25 GMT

Any help? awneil

RE: Best approach to interface HX711 with Nordic nrf52832?

faizi_968 — Fri, 21 Dec 2018 11:34:12 GMT

I can't seem to understand where it's getting stuck.

RE: Best approach to interface HX711 with Nordic nrf52832?

awneil — Fri, 21 Dec 2018 11:18:21 GMT

So use the debugger to see where, exactly, it is getting stuck!

RE: Best approach to interface HX711 with Nordic nrf52832?

faizi_968 — Fri, 21 Dec 2018 10:01:56 GMT

awneil, I can't seem to understand what the problem is. I have copied and pasted everything. It didn't work. It's not crashing, it's just getting stuck inside that function and I cant detect the problem either.

RE: Best approach to interface HX711 with Nordic nrf52832?

awneil — Thu, 20 Dec 2018 18:28:46 GMT

So what debugging have you done?

[quote userid="71471" url="~/f/nordic-q-a/34112/best-approach-to-interface-hx711-with-nordic-nrf52832/162722"]When I comment out the function "hx711_init(INPUT_CH_A_128, hx711_callback)" , code starts running smoothly[/quote]

So that's clearly an area to focus your debugging: is it getting stuck, or crashing in that function ... ?

RE: Best approach to interface HX711 with Nordic nrf52832?

faizi_968 — Thu, 20 Dec 2018 16:49:40 GMT

Hi Vidar Berg, This example is amazing. However, I am having issues using this example. I modified the "ble_app_uart" example from Nordic SDK, and included your portion of the code (As you have done), upon compiling, the nRF52832 DK does not advertise nor does it perform any other function. When I comment out the function "hx711_init(INPUT_CH_A_128, hx711_callback)" , code starts running smoothly, advertising is ok too. So what do you think seems to be the issue. Please help me. I am using Keil MDK-ARM 5, SDKv15.0.0, nRF52832 DK. Thanks

RE: Best approach to interface HX711 with Nordic nrf52832?

Droidik — Mon, 03 Dec 2018 10:13:47 GMT

Vidar Berg, once again thank you for your amazing work and support.

RE: Best approach to interface HX711 with Nordic nrf52832?

Vidar Berg — Mon, 03 Dec 2018 08:28:58 GMT

Droidik, the hx711_sample() function needs to be compiled with optimization to work when PD_SCK frequency is 1MHz. I suspect it would not have been necessary if I had rewritten this line "m_sample.value |= (nrf_gpio_pin_read(DOUT) << (23 - i));" to something more efficient.

RE: Best approach to interface HX711 with Nordic nrf52832?

Droidik — Sat, 01 Dec 2018 12:16:04 GMT

Solved by turning on the optimizations. Interesting.

RE: Best approach to interface HX711 with Nordic nrf52832?

Droidik — Fri, 30 Nov 2018 22:40:27 GMT

Vidar Berg
I just wanted to thank you for the provided sample code.
"Just keep in mind that the implementation should account for higher priority interrupts such as radio events that may occur during ADC readout."

I'm receiving DATA_ERROR in the callback every time. I think it's because of the BLE interrupts. What's the best solution to this problem in general?

RE: Best approach to interface HX711 with Nordic nrf52832?

Vidar Berg — Fri, 02 Nov 2018 09:02:50 GMT

Hello,

Unfortunately, the code was written for the nRF52 series. The same approach will not work on the nRF51 series as it doesn't have the PPI "fork" feature. Have you decided on using the nRF51? nRF52810 is a low cost alternative.

RE: Best approach to interface HX711 with Nordic nrf52832?

Pim — Thu, 01 Nov 2018 16:15:40 GMT

Hello Vidar Berg, thank you for this code! I'm trying to get it to work within KEIL5, however it does not compile.

Can you tell me which SDK version you wrote this for? It seems like NRF_GPIOTE is no longer available in the S130 soft device if I interpret the compilation errors correctly. Do you have any suggestions as to how to adjust this to a newer version? Please see the screenshot attached.

With kind regards!

RE: Best approach to interface HX711 with Nordic nrf52832?

anuragshukla — Mon, 07 May 2018 11:34:13 GMT

Thanks a ton Sir , I will definitely go through the datasheet and would try to create own code with reference to your code .
I would comment down below if I face any hurdle to implement the same.

RE: Best approach to interface HX711 with Nordic nrf52832?

Vidar Berg — Mon, 07 May 2018 08:55:29 GMT

Hi,

Please refer to the datasheet for the hx711, it does not use a standardized serial interface such as UART or TWI, which means that it has to be implemented in software (i.e., bit banging).

We don't have an official reference example for this ADC, but I have played with it in my spare time, see attached code. Documentation for this code is lacking, and I haven't done any thorough testing of it, but hopefully it can serve as a starting point. You can find other examples as well if you do a google search for hx711 and nrf52/51. Just keep in mind that the implementation should account for higher priority interrupts such as radio events that may occur during ADC readout.

devzone.nordicsemi.com/.../hx711.c devzone.nordicsemi.com/.../hx711.h

Update 9/11-18:

I've included an example in this thread: https://devzone.nordicsemi.com/f/nordic-q-a/40271/timer-issue-with-hx711---stopped-by-vector-catch-error