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WL1807MOD: DHCP server not working in Wifi AP mode when SDIO clock frequency is 50MHz

Part Number: WL1807MOD
Other Parts Discussed in Thread: WL1837

We were working on TI’s WL1807MOD wilink8 module. The module is working fine in station mode when clock frequency is 50MHz,( i.e when it supports the high-speed mode). In AP mode, we are able to connect to the AP , but the DHCP server is not able to receive DHCP request packet from the connecting station, though the DHCP offer is sent from the module. But when we changed the frequency to 25 MHz ( i.e disabled the support for high-speed mode), then the DHCP server is working fine in AP mode. We are able to receive DHCP request  and DHCP ack packets. But later, we see so many retransmission packets receiving in the wilink module.

Initially we suspected either it was a power supply or calibration issue. Inorder to confirm that there is no power supply issue we had tried by adding one 100uf capacitor at the 3.3V supply of the wifi chip. But still same behaviour. The DC/DC converter generating 3.3V is capable of delivering 3A and we did the load regulation test upto 2A for the same. We don’t think that the issue might be due to power supply or calibration. If it is power supply issue we will not be able to connect it and calibration issue normally create range problems. Since we are testing with device close to each other calibration issue will not affect. We had captured all the data lines and clock. To reduce the overshoot & undershoot we had added different values of termination resistors , waveforms smoothened but there was no change in the behaviour. The rise & fall time, delay between clock & data lines are less than 1ns.

 

We have attached the logs taken using gLogger app for the chip in AP mode in both frequencies.  We are not able to make out why the DHCP server is not working in 50MHz. Could you take a look at the logs and understand why could be that the DHCP server doesn’t work in 50MHz frequency and in 25MHz frequency, lots of retransmission packets are received? Schematic details are also attached

ap_dhcp_success_25MHz.csvap_dhcp_fail_50MHz.csv

  • Hello Khadeeja,

    I apologize for not getting back to you sooner, this ticket was incorrectly assigned. 

    It would be interesting to see behavior at 10MHz and/or lower. If AP begins working at lower speeds, that might suggest some sort of layout/timing issue. Could you also provide linux kernel version and wl18 firmware version? 

  • Hi Sabeeh,

    Our device has IMXRT1170  controller running on FreeRTOS and uses custom wifi stack. The wl18 firmware version we are using is Rev8-9-0-0-78 . Station mode is working fine in both 25 and 50 MHz. DHCP server in AP mode is having the issues.


    About  lowering the frequency , we'll check on that and let you know the results. 

    Regards,

    Febin

  • Hey Khadeeja,

    Thanks and let me know how it goes. In the meantime, I'll be reviewing your logs and discussing with other members internally. 

  • Hi Sabeeh,

    I tested with clock frequencies 400KHz, 5Mhz, 10MHz, 48,MHz, 49MHz. All are showing similar behaviour as above mentioned i.e station mode  is working fine, able to connect in AP mode and DHCP server is working,but a lot of retransmission packets are receiving in the controller after address assigned.
    I tested with 50MHz,and 51MHz also. Here station mode is working fine, we are able to connect in AP mode, but DHCP server handshakes are not completing. therefore address not assigned.

  • Hey Khadeeja,

    I believe the issue here lies within your custom wifi stack. Looking through the logs, I don't see anything out of the ordinary. My only concern here is that the firmware is quite old, so you might want to try upgrading that. However, I don't think firmware upgrade would resolve this particular issue, so this issue must lie in the FreeRTOS stack. Unfortunately, TI does not have a FreeRTOS stack for WL18xx and so our support is limited here.  

  • The wifi stack is  using a default WL8 configuration for the module WL1837 in our WL1807 chip. I hope that's all right.

  • Hey Khadeeja,

    I understand but the issue seems to lie in your WiFi stack itself, and that's not something that TI has support for. If you think it's a hardware issue, then certainly we can review that.