de-activating ARD

[o.hojvat]

Reference: first consult as Case id. 305571
Replyed by Tobjorn

I have a working proyect in wich 485 cable communication was replaced with NRF24L01+ but I need some help:

One PTX has bi-direccional comunication with several PRX in a sequential order as original schema for 485

PTX changes address using diferent ones for each PRX and had used PIPES 0, 1 and 2 in each PRX

Data can be sent from PTX and replied from PRX as ACK payload , automatic payload length.

Most usually there are 1 to 6 bytes ack payload at 1Mhz and it works fine with 250us ARD

For 8 bytes in the ACK payload ARD needs to be increased to more than 500us  as data sheet states 

 When testing with 8bytes of course default 250us  was not  suficient and not ACK was received in PTX (never)

At first I try to deactivate the automatic retrasmition with 00 value in Reg.04 but it remains with no ACK

Default is hex 03 -> 250us ARD and max.retry 3

It works fine with hex 10 or 20 and I left 20 for 750 us and no retry

--- Please explain me the reason of having no results with 00 value.

__________________________________________________________________

Monitoring RX packets:

I have used a separeted PRX device (Monitor) setted for no ACK and with the same address as the PRX under test

In this Monitor I can found at SPI MISO the packets sent from PTX but not the normal ACK payload reply

I guess there is a diferent format but I can´t find information in data sheet

But when there is the case of default 03 value in Reg04, I can see the original packet from PTX
and the 3 retryedACK Payload after the ARD elapsed !!!

I veryfied with hex 05 in PTX Reg04 and number of packets changes to 5

It seems to be diferent packet format for PTX tx sent , ACK payload and the retryed ACK payload

--- Please explain me if there are some way to observe the ACK Payload in a separate PRX device.

I can send some captures with Saelae 8 ch and with Kingst LA1010 if someone asks.

Best Regards, Osvaldo Hojvat

[Kenneth]

Hello,

We don't provide support for the nRF24L01+ anymore, but some comments:

If you want to receive an ACK payload, the ARD delay need to be set accordingly to the ACK payload size (even if the number of retransmissions are 0).

If you have two PRX with same address, then this will cause issues, because both PRX will try to ACK, the two ACK will collide on-air and likely cause the PTX from receiving any ACK.

Kenneth

[o.hojvat]

Thak you for the reply.

I have a second PRX with same address but ACK disabled.

Ÿou had confirmed what I guess about ARD settings.

Data sheet do not mention that ARD is not disabled with Reg.04 = 00.

I find  other unexpected thing 

In some specific mensaje there is an ACK received at the expected time but there is not an IRQ at the PRX, so PRX lost ínfomation

This arises about 3 times each 10 so it is no problem for me. Request info again.

Best regards. Osvaldo

[o.hojvat]

upper channels for PTX (named MIRF)

lower for PRX (Mando)

marked with white rectangle , there is no IRQ at PRX but there is ack and payload at PTX

[Kenneth]

o.hojvat said:

I have a second PRX with same address but ACK disabled.

A PTX can choose to disable ACK when transmitting a packet, but a PRX will always ACK if requested by a PTX.

A PRX may not generate an interrupt if the received packet is considered the same as a previous packet from the PTX.

Kenneth

[o.hojvat]

Hi Kenneth

Thank you for your comments.

About ACK ok but no IRQ I may investigated more when I will finish solving many details in my proyect.

About the PRX I used as Monitor ,I is working with not sending ACK as you can see in th attached pdf , LA1010 capture.

There are .txt explaining the picture and the instructions sent for NRF setting.

Anyway this Monitor PRX only can receive the PTX packets.

In a before sent picture with the normal PRX and the Monito PRX , I see in the Monitor several ACK sent when retry number was 3 or five because low ARD pevents ACK at PRT

This matter at the moment is not important to me because I guess I will no need more the Monitor PRX.

I have an NRF board with the Tx burned beacuse a short circuit.

I can use it in the Monitor PRX to be sure It can't Tx nothing

Best Regards, Osvaldo