Best way to send float over BLE

[Renix]

What is the Best way to send float over BLE?

Values range between -2.000volt and +2.000Volt (-2000mV / +2000mV) Do I break it into two uint8_t and manipulate the +/- sign in separate 8-bit byte?

I took the ble_sdk_app_proximity example, and commented out what I do not need. Then used the examples from the tutorials, to add three services. So I added x3 services, based on the BLE Characteristics, a beginner's tutorial, and it is working fine. (nrf5-ble-tutorial-characteristic-CompletedCode ported for SDK 13.zip)

So I need to send the Voltage either as a float, or manipulate it to look like uint8_t, and keep track of the sign.

Any help appreciated.

[ypearson]

You can use this function that encodes a float (32 bits) into a uint8_t buffer

bds_float_encode(&float_data, encoded_buffer)

A float after all is just 4 bytes of data.

The definition of the function is in this file

./sdk/components/libraries/util/app_util_bds.h

static __INLINE uint8_t bds_float_encode(const float_t * p_value, uint8_t * p_encoded_data){
union { 
    float float_val;
    uint8_t char_val[4];
}encoder;

encoder.float_val = *p_value;
p_encoded_data[0] = encoder.char_val[0];
p_encoded_data[1] = encoder.char_val[1];
p_encoded_data[2] = encoder.char_val[2];
p_encoded_data[3] = encoder.char_val[3];
return(4);}

.

[Renix]

Yvan, 2 questions:

1. The IAR compiler does not understand the union definition. Is there something missing. It is not clear how this gets implemented.
2. It looks like the code simply breaks the 32-bits up into 4x bytes of 8-bits. It is not IEEE-754 32-bit Single-Precision Floating-Point Number conversion?

Any help appreciated