Correct data for 0x29AD BLE Weight Measurement? Currently seeing no value

Question

Working with Arduino ESP32.

I managed to implement Environment temp + humidity using the specified BLE spec service and characteristic UUID's. I got lucky as I could see that the values were presenting wrong and could figure out what inputs were needed for correct outputs.

Now working with weight I am getting no value displaying for my weight measurement characteristic. I have the weight scale service (0x181D), Scale Feature (0x2A9E) and Weight Measurement (0x2A9D). I can send 0000 or 1111 to 2A9E to get a a formatted display of what the scale features are. Cool! I saw elsewhere on stack that having this characteristic set was required for the weight measurement to show.

I'm using 0000 as I don't need the timestamp or multi user. I've also read both datasheets (WSS_V1.0.0 & WSP_V1.0.0) for the characteristics I'm using and am still stuck. (WSS_V1.0.0 & WSP_V1.0.0)

WSS states the first byte sets the flags and the following bytes are for the weight. I've tried using

0000101010101010 == {0x0A, 0xAA} == 0000(flags) 1010(weight) ...

Which fits the format of 4 flag bytes followed by weight, followed by optionals.

still no luck. Online resources are limited, I've tried reading the docs and no examples are given.

Any help would be much appreciated and would assist in other looking for a similar answer

Answer 1

There's an example that has working code for those who stumble into this thread later down the line.

https://github.com/bneedhamia/CurieBLEBowlScale/blob/master/CurieBLEBowlScale.ino

A weight measurement has it's first byte dedicated to flags

/*
* Set the flags:
* bit 0 = 0 means we're reporting in SI units (kg and meters)
* bit 1 = 0 means there is no time stamp in our report
* bit 2 = 0 means User ID is NOT in our report
* bit 3 = 0 means no BMI and Height are in our report
* bits 4..7 are reserved, and set to zero.
*/

flags |= 0x0 << 0;
flags |= 0x0 << 1;
flags |= 0x0 << 2;
flags |= 0x0 << 3;

and the following two bytes contain the weight in big Endian.

  bytes[0] = flags;

  // BLE GATT multi-byte values are encoded Least-Significant Byte first.
  bytes[1] = (unsigned char) newVal;
  bytes[2] = (unsigned char) (newVal >> 8);

  chrScaleValue->setValue(bytes, sizeof(bytes));