Purpose of PPP field in nRF24L01+ W_ACK_PAYLOAD command?

[laneh]

In the mRF24L01+:

Unlike MultiCeiver mode, I have one TRX and multiple PRX units sending back ACK payloads.

In the PRX, what is the purpose of the PPP field in the W_ACK_PAYLOAD command? If the PRX returns an ACK packet using the same address it responded to, why would a pipe number matter?  Is the PPP field used only for MultiCeiver systems?

[laneh]

Hakon,

Again thank you for a quick reply. 

I do understand that the receiver must pre-load the ACK packet and that is why my first diagram says the ACK payload "was loaded" to mean before receipt of the transmitted packet. This question was actually answered in a previous ticket.

My scheme is similar to your suggestion but uses less air time. The purpose of the "broadcast" address (pipe 1) and the transmitter loading the "...NO_ACK" FIFO for this address (pipe 1) is to tell every receiver at once to update its ACK payload. Then the transmitter can address each receiver individually to retrieve each receiver's ACK data. 

[Håkon Alseth]

Hi,

 

laneh said:

I do understand that the receiver must pre-load the ACK packet and that is why my first diagram says the ACK payload "was loaded" to mean before receipt of the transmitted packet. This question was actually answered in a previous ticket.

My apologies, I missed this. Its good to hear that you have control over the radio low level behavior!

 

laneh said:

My scheme is similar to your suggestion but uses less air time. The purpose of the "broadcast" address (pipe 1) and the transmitter loading the "...NO_ACK" FIFO for this address (pipe 1) is to tell every receiver at once to update its ACK payload. Then the transmitter can address each receiver individually to retrieve each receiver's ACK data. 

 This is a good solution, but be careful if one of the receivers doesn't catch the broadcast'ed payload.

 

Kind regards,

Håkon