CC2545: CC254x(CC2545) PER problem.

Have you checked more frequencies than the two?

I suspect that you have more noise on the first channel compared to the second. Do you see the same if you have the devices placed next to each other?

Yes, I have checked every freq. include 2388MHz and 2490Mhz.

When testing, I turned off all wifi device.

The situration is the same. First packet is always lost and I could find out the problem. 

Even I changed code development.

Austin

Have you tested what happens if you use the same frequency for the two packets?

The result is the same. First packet still lost, second packet still good.
I also exchanged ID words etc.

Not easy to understand what's going on based on the description.
- The RX side, I assume that is on continuously? If not, have you checked the timing?
- For the packets that has CRC errors for the first packet you send, are you able to identify where in the packet you get bit errors and if these are on the same place each time?

RX timing is setup by Tx first byte.
Please refer the picture. I have checked timing many times and it is correct.

My issue is, I cannot understand " First packet always lost (over 5%), second packet almost good (near 0%)".

Also I found, first packet SYNC words always lost, not CRC error.

Could you elaborate a bit on the drawing?
- What is timing adjusted vs not adjusted
- What is RX receive packet all time, does that mean no packet errors?
- If the sync word is lost it could sound like a timing issue. How have you tested that the timing is ok?

Hi
When system on, the status is unknown.
Also, the RF situation is unknown, too.
Because that, Rx should stay in one frequency to try to receive correct data.
Before Rx received data, I called it not adjusted.

After Rx received data, I called it adjusted.
When Rx adjusted, you can find in my drawing, Rx always leading Tx transmit.
Tx transmit in Time1 & Time3. Rx receive start at Time2&Time4.

In usually, the sync word lost all about timing issue, but not in my case.
The reason as below
1. I have checked timing many many times.
2. Tx distance Rx in 3meters, fist packet is good(near 0%)
3. Tx distance Rx over 5meters, first packet is poor (PER over 5%)
Because reason 2&3, I can very sure to tell you, not timing issue.

Austin

When you test @3 m vs > 5 m, is it any difference between RSSI on the first and second received packet?

I don't see why signal strength should be a issue for packet 1 and not for packet 2.

Hi Ter
I don't know how to explain all things.
If I can resolved this problem easily, I will not be there.
This is not about RSSI or timing problem, because I checked all things.
When I use antenna to test these, it may have signal strength problem.
So that, I used cable and attenuator to test these around 2 weeks ago.
Also, I guess that maybe my PCB has design issue or else, so I checked it by TI development kit.(SmartRF05EB & CC254xEM)
The result is the same.

Austin

I assume you have done a lot of tests in the weeks you have worked with this but remember I have not seen any results from the testing other than the results you give here. Also I have to ask a lot of questions to get a picture of what it looks like in your end.

- Is it some way we can recreate what you are seeing in our lab?

Can I send you the code and related information to help identify the problem?
If you can, please provide your E-Mail, thank you.

The easiest would be if you send me a friend request here on the forum and then send me the code as a private message.

I accepted your request but I don't think I have received any code. Has the status on this changed?