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Almost decent scale

Work in progress, a clone of decent scale for home use

BOM:

  • ESP32 or esp32-s3-mini
  • HX711
  • Load cell (either 500g or 750g) - take care of screw location / orientation, this will affect your enclosure choice.
  • some M3 flathead and countersunk screws you probably have lying around
  • M3 threaded inserts if you're going with the 500g design.

Designs / Enclosures

Currently, two enclosure designs are available in this repo. A build for esp32-s3-mini and a build for esp32, provided by @randomcoffeesnob. The design for esp32-s3-mini is still under active development, while the esp32 and 500g load cell is ready to go!

Pick the one you want, based on the equipment you have. But be wary, esp32-s3-mini design is really not finished yet!

Calibrating over Bluetooth:

The scale supports calibrating over bluetooth. To calibrate the scale, send the 0x03F1 command to 36F5 which will activate the calibration mode.

Once in calibration, the process is the same as when calibrating over Serial port.

  • remove all weights and wait for the scale to tare (7 seconds)
  • add a known weight
  • read the value from the control characteristic 36F5, I copy the value into calculator on macOS, use byteflip and change to decimal representation.
  • calculate the factor: (units_read_from_char / known_weight)
  • write 0x03F2XXXXXXXX to 36F5 where XX is the uint32(hex) representation of the factor multiplied by 1000 (i.e. 0x03F20000073A for factor 1.85). Make sure to pad the value with any leading zeroes you need.
  • scale should be calibrated now

TODO:

  • conform to DE scale BT protocol (tare, led, version, etc) ✔️ looks ok
  • Add own thread logic
  • Calibration over BT ✔️
  • DE1 tare command handling ✔️
  • esp32-s3 target ✔️
  • (maybe) web server
  • esp32-s2 mini target <- cancelled, only has wifi, maybe one day s3-mini
  • esp32-s3-mini ✔️

Use platformio.ini to define pins for your setup. Also if you want to use fake BT for some reason, add -D BT_COMMS_FAKE, otherwise use -D BT_COMMS_NIMBLE.

Additionally, I had to slow down my esp32s3 devboard - use -D ESP32S3_SLOWDOWN to reduce clock speed to 80MHz.