Empty packets received occasionally on BL653

[Dagan Raviv]

Hello,

I'm working with nRF52840 for some time, communicating esb on a BL653-DK (Laird), trough nRF52840dongle.

Recently I noticed that during ongoing communication, occasionally a packet is received on the BL653 with length 0

(in "esb.c" file, in 'esb_read_rx_payload' function: payload->length == 0), while all packets are sent correctly from the dongle,

and also received and read correctly by my esb sniffer app.

The timings of these received empty packets are within expected time gaps, and it occurs every few hundreds of milliseconds, every few tens of packets.

Any guess on what can be the cause of this issue, and if and how it can be avoided? 

Thanks in advance!

[Håkon Alseth]

Hi,

 

A zero length packet is normally an ACK.

Are you having several PTX communicating towards one PRX? If yes, do the PTX devices have an unique RF address?

 

Kind regards,

Håkon

[Dagan Raviv]

Thanks for your response,

I'm using only one PTX with one PRX device. The packets are being broadcasted over the same RF channel, and the zero sized packets are received every once in a while when a "normal" packet was sent from the PTX.

[Håkon Alseth]

Hi,

 

Q1: Could you share your esb configuration?

Q2: Which NCS version are you using?

Q3: Is this issue reproducible on a nRF52840-DK? 

 

If you are using the default address (0xe7e7e7e7), there could be other devices in your area that is also using this address space, which will influence your overall communication.

 

Kind regards,

Håkon

[Dagan Raviv]

Hi, 

1. This is my esb configuration:

struct esb_config esbConfig = ESB_DEFAULT_CONFIG;

...

    esbConfig.protocol = ESB_PROTOCOL_ESB_DPL;

    esbConfig.retransmit_delay = 100;

    esbConfig.tx_output_power = ESB_TX_POWER_4DBM;

    esbConfig.retransmit_count = 0;

    esbConfig.bitrate = ESB_BITRATE_2MBPS_BLE;

    esbConfig.event_handler = EventHandler;

    esbConfig.mode = ESB_MODE_PTX;

    esbConfig.selective_auto_ack = false;

2. I'm using ncs version 1.9.1

3. Unfortunately I don't have a nRF52840-DK, but on a Laird BL653-DK this issue does not occur.

I am using the default base address, but also using address 0xc2c2c2c2 as base_address_1 and assigning 0xe7c2c3c4c5c6c7c8 as prefixes.

Thank you for your assistance,

Dagan

[Håkon Alseth]

Hi,

 

Dagan Raviv said:

esbConfig.retransmit_delay = 100;

This is not a valid range, here's the minimum:

https://github.com/nrfconnect/sdk-nrf/blob/v1.9.1/subsys/esb/esb.c#L35

 

Can you adjust this delay to 600 and see if the issue still occurs?

 

Kind regards,

Håkon

[Dagan Raviv]

Hi,

I changed the value to 600 on both ends, yet I am still getting empty packets instead of "real" ones once in a while...

Any more ideas?

Kind regards,

Dagan

[Håkon Alseth]

Hi,

 

Do you see this issue if you use the stock (unmodified) PRX and PTX samples?

 

Kind regards,

Håkon