Documentation tracking

[kesyog]

• Calibration instructions
• Board errata
• Do a pass of rustdoc comments

[cicatrix87]

Are you still working on a documentation? I would like to build some of those devices for a few friends, but how its now im a bit confused what and how to do it.

[kesyog]

Hey, I wasn't planning on writing step-by-step detailed instructions for building these. The process is a bit involved, especially if you don't have soldering and embedded experience and equipment. Also, I'd rather steer people toward getting a Tindeq to support their product.

I am planning on writing a high-level guide to document the project further and steer people around some of the obstacles I ran into. It'll live in the attached page, https://kesyog.github.io/hangman. Unfortunately, it's hard to find the time and energy to do this sort of thing so I probably won't get around to it for a while (likely on the order of months at least).

That said, if you do have the background, curiosity, and time to fill in the gaps, the quick summary:

1. Buy this crane scale: https://www.amazon.com/dp/B07MTFXSJW
2. Order the PCB's and electronic parts. I can dig up a parts list if you're interested.
3. Assemble the PCB, ideally with SMT soldering equipment.
4. Replace the existing PCB in the crane scale with your PCB and solder the load cell and battery wires to the PCB.
5. Flash the s113 NRF SoftDevice image using nrfjprog --family nrf52 --program <path to hex file> --chiperase --verify. I used a Segger J-Link for flashing.
6. Install Rust
7. Build and flash the image. The repo is set up such that cargo run will build the image and use probe-rs to flash the image.
8. Perform two-point calibration over BLE: https://kesyog.github.io/hangman/calibration.html
9. Enjoy.

Hope that helps!

[cicatrix87]

I already have a similiar crane scale that could work, in the end those load cells should work identical or? I will check if the originial PCB in this one has the same dimensions and screw points as yours. A Parts List would be highly recommended so a BOM&CPL that i could order everything together with the PCB. Sure i could buy a Tindeq but its more fun like this,

[kesyog]

It'll almost certainly work with a different load cell as essentially all load cell circuitry works the same way. Most cheap ones have the same 4-wire connection. Some more expensive ones have an additional two sense wires and/or an extra shield line, especially if they have a long cable, but shield can be tied to ground and IIRC the sense lines can either be ignored or tied to the corresponding +/- output lines.

Some things to look out for if you're using a different load cell:

• I'm guessing the the board size and screw points will be different. If needed, you could re-design the boards using the same schematic files to fit the new part. The layout is pretty spacious so there's lots of leeway to move components around to fit a shape
• Make sure the crane scale housing is plastic, not metal, so that it doesn't block wireless transmission.
• Ideally, put the BLE antenna as far away as possible from the metal load cell. I'm not sure how much this matters for the purposes of the crane scale use case where we're probably only ever transmitting over a few meters, but the datasheets recommend keeping the antenna away from metal.
• Make sure the max battery voltage is okay for the nRF52832 microcontroller
• Don't worry about the load cell weight rating. The firmware doesn't care. Once you calibrate it, things should just work, whether you're using a 50kg load cell or a 1000kg load cell.

Also, you'll need a known weight to do calibration, so it's helpful to have an unmodified crane scale (or any kind of scale) to measure your calibration weight.

Here's the part list I used:

Part	Ref des	Part number/Digikey part number	Notes
SWD connector		1849-PM20B05VBDN-ND
Fanstel BT module		BT832	https://www.fanstel.com/bt832-1-1
Push-button		2223-TS02-66-70-BK-160-LCR-D-ND
TI ADC		ADS1230	https://www.digikey.com/en/products/detail/texas-instruments/ADS1230IPWR/1689136
PFET	Q1	SSM3J378RLFCT-ND
32.768kHz crystal		SC32S-7PF20PPM	https://www.digikey.com/en/products/detail/seiko-instruments/SC32S-7PF20PPM/4931504
RLED	R8	RMCF0805JT100RCT-ND	(for debugging)
LED		3147-B1911USD-20D000114U1930CT-ND	(for debugging)
10pF	C1 C2	1276-1069-1-ND
0.1uF filter caps	C6	490-GRMJN65C1H104JE01JCT-ND	https://www.digikey.com/en/products/detail/murata-electronics/GRMJN65C1H104JE01J/19115572
10nF filter caps	C3 C7	490-GRT1885C1E103JA02JCT-ND
0.1uF	C4 C5	1276-1935-1-ND
10uF	C8 C9 C10	1276-2399-1-ND
47	R4 R5 R6 R7	RMCF0603FT47R5CT-ND
100	R1 R2	RMCF0603FT100RCT-ND
49.9k	R3 R9	RMCF0603FT49K9CT-ND

Let me know if/when you get it working. I won't be able to give too much debugging help, but I might be able to point you to relevant docs I found helpful.

[roviraleix]

Hello,

any updates on it? I've got an nRF52840 board and a HX711 and would like to try to make it work with the tindeq app. Just adding this 2 components to the crane and leaving the original board.
I was wondering if it would be possible to flash the nRF with the tindeq firmware.

Regards and congrats for this nice project!