HX711 Driver (My first PASM code!)

msg558

Hello all. I've been playing with the propeller 1 off and on for many years now and PASM always seemed like complete wizardry to me. I'm currently involved in a project where I need to read load cells and found the HX711 breakout modules online for cheap, but there didn't seem to be a driver for the propeller yet. The communication protocol for the HX711 seemed simple enough so I decided to give it a shot in PASM and was able to produce a working result!

I'd like to share it with others and get it posted to the OBEX, but wanted to see if there was any constructive criticism first.

JonnyMac

I wrote a Spin1 object for the HX711 for a work project, and then translated it to the P2 where I converted the Spin1 SPI code to inline PASM2. You might find it interesting. What you'll note about PASM2 is that it's much more concise than PASM1.

Beau Schwabe

See my post here for any filtering ideas ....

https://forums.parallax.com/discussion/comment/1520585/#Comment_1520585

I designed a load cell combiner around the HX711 that communicated in "MODBUS" style packets to a main controller.

msg558

@JonnyMac

Very cool. I have yet to experiment with the P2, but the inline PASM seems like a huge benefit. Forgive my ignorance, but it looks like the bit-banging is happening in the spin code after the PASM, if so, what does that chunk of PASM afford you?

@"Beau Schwabe"

That's a pretty board, and I will certainly look to use that filtering if I need better sensitivity and response time. Are the MODBUS packets being generated on that board?

JonnyMac

Forgive my ignorance, but it looks like the bit-banging is happening in the spin code after the PASM, if so, what does that chunk of PASM afford you?

That section is commented out -- it was my reference for writing the PASM2 code above it. That PASM2 code is doing the work in that method.

msg558

That section is commented out -- it was my reference for writing the PASM2 code above it. That PASM2 code is doing the work in that method.

Of course it is. I would have noticed that had I looked at it in the prop tool instead of notepad.

Beau Schwabe

@msg558 said:
@"Beau Schwabe"
That's a pretty board, and I will certainly look to use that filtering if I need better sensitivity and response time. Are the MODBUS packets being generated on that board?

Thanks... Yes the response packets are generated on that board since it is operating as a slave. The request packets are generated on another board acting as the master.
On the slave board there is a 16F15323 programmed in pure assembly that talks to the HX711 and listens/responds to the MODBUS requests. There are about 10 different request commands that it processes.