Problem about proprietary protocol and ack

[chianglin]

Hi,

In my develop environment , there have many proprietary device.  One device is working on PTX mode, and the other devices is working in PRX mode.

If the PTX device send a broadcast proprietary packet (need ACK), all of PRX devices may  send ACK message back. Does it correct?

How can "PTX device" know the "ACK message" is send from which PRX device?

Thank you,

Chianglin

[Hung Bui]

Hi Chianglin, 

If you have multiple RX and one TX , I would suggest not to use require ACK packet. The PTX will switch of RX right after the first ACK packet received. 

My suggestion is to send it as a NO_ACK packet, but then switch to PRX mode and listen. 

On the normal PRXs when it receives a packet from the PTX, after giving a certain delay will switch to TX mode and send a (NOACK) packet back to acknowledge. In your packet you can add an ID of the PRX in the payload so that the PTX would know from where the packet comes from. 

[chianglin]

Hi Hung,

Thank you for your answer.

I still have following questions:

1. Would you please give me the bast and most quickly method to switch between PTX and PRX?

2.  if I have multiple TX and multiple RX node in the same position and all of the TX node send broadcast packet.  Does all of the RX node will receive these broadcast packet and send ACK packet back to TX node (if use require ACK packet)?.  Does RX node know the address of TX node by analyze the content of received TX packet?

3. Does the RX node can create a black-list of TX node?  I means: If the address of TX node is add into the black list of RX node, then RX will not receive any packet of this TX-node.

Thank you,

Chianglin

[Hung Bui]

Hi,

I have to correct my self, in last reply, the first sentence please read as "PTX will switch back to TX right after the first ACK received"

1. You can use a SHORT  to join END event and DISABLE task to disable TX after you sent and a short to join DISABLED event to RXEN task to start RX. 

2. You are talking about 1 TX talking to 1 RX and there are several pair of them ? The ACK packet is sent to the same address as it received. Note that there isn't a TX address and a RX address, they are the same on each pair. 

A PRX can have different address, but a PTX has only one address, it's the address it sends data to and receive ACK from. 

3. No. And as mentioned in 2, If there are multiple PTX sending to one address on PRX they all have the same address. But it's possible to disable a pipe, meaning you don't listen on that address anymore. 

[chianglin]

Hi,

Sorry, I have to explain the detail condition about previous question 2:

For example, there have 6 proprietary devices, 3 devices are working in TX mode (continue send PTX packet) and 3 device are working in RX mode (run in PRX mode).

a. Do these 3 PRX had received all of the 3 PTX packet and send ACK back to each PTX device?.

b. After each TX device transmits a PTX Packet, it will receive an ACK packet from "different RX devices"?

Thank you,

Chianglin

[Hung Bui]

Hi Chianglin, 

 

Let me explain you how it work with ESB (I assume you use ESB)

- A PRX device would have 8 pipes to receive data, each pipe has an address. It could be 2 or 3 bytes address, but let's think of them as address number 1 2 3 ...8. 

Each PTX device would have a TX address, and a RX address to receive ACK from, they are the same number. So if a PTX send a packet to address 2 on TX, it will expect to hear ACK that has address 2 on RX. 

And the address the PTX send to match with the address on the PRX, in this case number 2. 

In your case you have 3PRX and 3 PTX. It depends on how you configure it. If you configure all PRX to have same address, say number 3. And all three PTXs has address configure to 3. Then whenever a PTX send a packet, all three PRX will receive and send a ACK back. But it's where the problem is, if all of them receive and send at the same time, there will be collision and the PTXs wouldn't receive anything because messages are collided. Even if message was not  collided by somehow you implement a random delay (as suggested) the PTX wouldn't listen after it gets the first ACK. So no, a PTX can't receive ACK from multiple PRX. You need to switch it to PRX to receive. 

Also another note is that PTX will not listen if it's not expecting ACK. So when a PTX not sending data, it will not receive anything.