Sending Integers with Nrf24L01

Wireless & IoT
1

This might be simple but i can’t seem to figure out how to send a 3 or 4 digit number between to NRF’s. I can send unsigned characters just fine but I can’t seem to send integers. Is this a problem with SPI?

2

Uhm… NRF’s just chuck bytes back and forth. They don’t care whether they map to a valid ascii character or not.

An unsigned int is typically just 4 bytes representing that value. Break it down into the constituent bytes, and send individually.

For example:

unsigned char m[4]; // message of length 4 bytes

m[0] = value >> 24; // No need for & 0xFF masking, will be clamped by type conversion
m[1] = value >> 16;
m[2] = value >> 8;
m[3] = value;

send_message(m)

To reconstitute on the other end:

unsigned int value = 0xCAFEBABE;
unsigned char m[4]; // message of length 4 bytes
recv_message(m)

value = ((unsigned int)m[0] << 24) | ((unsigned int)m[1] << 16) | ((unsigned int)m[2] <<8) | m[3];

value == 0xCAFEBABE

Note, I haven’t tested this specific code, so typos may be present.

Also note that a full 4 byte unsigned integer will represent the range from 0 to 4294967295, which may be unnecessary in your application. If you don’t need that range, and message size is a concern, just send 8, or 16 bit integers, for ranges of 0-255, or 0-65535.

3

I will have to give a try tonight and see what happens.