Android BLE : Weight data from the BLE Scale - Need to convert byte array to decimal weight value in Kotlin

I connected my app with a BLE weight scale device and I'm able to get the byte array from the device.but I couldn't able to convert the byte array to my weight.
the weight value is coming in the 6th position of the byte array. I have some test cases as follows.

[-6, 5, 0, 3, 0, 0, 32, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] =========32gm

[-6, 5, 0, 3, 0, 1, 108, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] ========364gm

[-6, 5, 0, 3, 0, 0, -17, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] ========239gm

[-6, 5, 0, 3, 0, 1, 108, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] =======364gm

[-6, 5, 0, 3, 0, 1, 69, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] ========325gm

[-6, 5, 0, 3, 0, 1, 77, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]==========333gm

[-6, 5, 0, 3, 0, 2, 91, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] =========603gm

[-6, 5, 0, 3, 0, 4, 16, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] =========1040gm

It seems like 5th and 6th values are dependent.Please help me on converting this to weight value.

The data you want to receive is a Short value stored in two bytes at position 5 and 6. The easiest way to decode bytes to primitive in kotlin jvm is to wrap this part of the data into a ByteBuffer and decode it.

From one of your line

> [-6, 5, 0, 3, 0, 1, 108, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] ========364gm

val bleByteArray = byteArrayOf(-6, 5, 0, 3, 0, 1, 108, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)
val buffer = ByteBuffer.wrap(bleByteArray, 5, Short.SIZE_BYTES)
assert(buffer.getShort() == 364)

Here, buffer only contains bytes 5 and 6. So when getShort is called, the buffer read the first two bytes and return the corresponding short value.

If you want to read other parts of the ble information, you may want to wrap() the whole ByteArray and then read multiple parts of it with other methods of ByteBuffer.

Assuming the incoming data is typed as byte[32] and saved into an array named ble:

int weight = (ble[5] << 8) | ble[6];

Remember that Java arrays start with index 0, so the first element is ble[0], not ble1. That's why the above code uses array elements 5 and 6 - they are actually the 6th and 7th elements of the array.