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Topic: Can an HX711 work on D1 (TXD) (Read 176 times) previous topic - next topic

aiannar974

Hello - I am running a pro mini with 4 load cells.  I have used every pin except A6 at this point.  I did not pick load cell 1 to be connected to D1 for any reason in particular, but it is the only load cell that freezes the code.  Can a bad HX711 cause this issue?

Thank you,

Anthony


Wawa

Four HX711 boards.
That's five Arduino pins.
What else is connected?
Leo..

aiannar974

Hello Leo - I have 4 start buttons, 1 yes button, 1 no button, 4 load cells (8 pins - 4 clk and 4 dout), 1 pot, 4 relays, LCD I2C display (2 pins, a4 and a5)

How do you only use 5 pins for 4 load cells?

Anthony

Wawa

No practical experience with multiple HX711 boards, but it seems you can share the CLK pin.
Look at the HX711 multi library.

I see in your previous thread that you're using a 3.3volt ProMini.
Did you use HX711 boards with separate analogue and digital VCCs.
The analogue part of the HX711 MUST have a 5volt supply for a stable load cell excitation voltage.
Leo..

aiannar974

Hello Wawa - Wow you are thorough.  I am using the 3.3v,  I read that the hx711 would run on 3.3v 


https://forum.arduino.cc/index.php?topic=433015.0

I do have 5v on this project that I could get to the hx711s but the other 3 seem to be fine.

I didn't know clk can be shared.  Do I need to do anything special like turn a pin on or off?

Anthony

Wawa

The last post in that link lowers the excitation voltage.
That also lowers load cell sensitivity. Not good if you have a 5volt supply available.

It shouldn't be that hard to separate analogue VCC and digital VDD of a HX711 board.
We might be able to help you with that if you can cut tracks and solder wires to the board.
Post clear pictures of both sides of the boards you have.

Sparkfun sells HX711 boards designed for 3.3volt logic.
VCC being the 5volt analogue/load cell supply, and VDD the digital 3.3volt (or 5volt) supply.
Leo..

aiannar974

This is the 3rd case of needing 5v on this project.  I think I will change to a 5 volt board. 

As far as the d1 for a load cell, is there an issue with this?  just curious.  I can either switch it out or use the common clk pin that will free up 3 pins.


Anthony

Wawa

D0, D1 are the hardware serial pins.
Not sure if it's a problem with the ProMini (without USB<>Serial chip), but you should avoid those if you can.
The SCK pin (pin13 on an Uno) could also create problems on small Arduino boards when used as input.
Leo..

aiannar974

Luck of the draw, I used pin 13 as an input on my first test of this project.  Took a while and help from this forum to figure it out.  I moved it to an output.  The other thing that through me for a loop was the A6 and A7 pins can only be analog

Anthony

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