S0 and S1 fields

RE: S0 and S1 fields

George555 — Sat, 04 Apr 2020 14:50:38 GMT

In the example I used as a base, S0, S1, and LENGTH fields are equal 0.

RE: S0 and S1 fields

Dmitry — Sat, 04 Apr 2020 13:21:43 GMT

If you have length field encoded in the first byte of packet, or payload length is static, you don't need S0.
S1 is only needed as padding if your LENGTH field is less than 8 bits (I believe it's not).

RE: S0 and S1 fields

George555 — Sat, 04 Apr 2020 13:12:23 GMT

Thanks Dmitry,

Do I need to use them in case I want to implement my own protocol with static or dynamic payload length?

I have modified a simple example with static packet payload length and it works fine. I'm just not sure if I need those fields.

RE: S0 and S1 fields

Dmitry — Sat, 04 Apr 2020 12:23:22 GMT

Hi,
these fields allow radio to work with different protocols and packet formats.
S0 is a part of packet preceding length field (e.g. in BLE, length field is the second byte). Thus receiver/transmitter knows where to look for packet length.
S1 is to handle cases when packet header is not a multiple of byte (in ESB, for example, PCF field is 9 bits wide).