Wrong nRF21540 signals on custom board

[Benno Trutmann]

Hi.

I try to activate the nRF21540 on a custom board, based on the nRF5340 Audio sample in BIS gateway configuration. I tested the sample code on the nRF5340 Audio DK with the nRF21540 EK shield. In this configuration the sample works and the relevant nRF21540 signals look as below:

On our custom board the nRF21540 signals are on different nRF5340 pins and therefore I added the following to our board device tree (the nRF21540 SPI signals are not used by the sample code, so I put SPI_CS fix to high and SPI_SCK, SPI_MOSI, SPI_MISO fix to low):

    gpio_fwd: nrf-gpio-forwarder {

        compatible = "nordic,nrf-gpio-forwarder";

        status = "okay";

        nrf21540-gpio-if {

            gpios = <&gpio0 30 0>,  /* tx-en-gpios   TP26 */

                <&gpio1 12 0>,      /* rx-en-gpios   TP20 */

                <&gpio1 10 0>,      /* pdn-gpios     TP19 */

                <&gpio0 31 0>,      /* ant-sel-gpios TP27 */

                <&gpio1 13 0>;      /* mode-gpios    TP21 */

        };

    };

But with this configuration the nRF21540 signals look totally different and there is almost no RF signal (< -80dBm):

Without nRF21540 our board streams audio correctly.

How do I get our board working with nRF21540?

Regards,
Benno

[Vidar Berg]

Update: The developer seems to have found the problem, but it looks like it might require a new controller release to fix, unfortunately. Turns out the controller had LED indications enabled on P0.28-31. These should not have been enabled in the release.

He's currently investigating whether there may be a workaround for this.

[Vidar Berg]

A workaround while waiting for a new controller release is to map the LED indication to an unused pin:

Please suggest customer to modify the controller_leds_mapping() to:

static int controller_leds_mapping(void)
{
    int ret;
       ret = ble_hci_vsc_led_pin_map(PAL_LED_ID_CPU_ACTIVE,
                                     PAL_LED_MODE_DISABLE_TOGGLE,
                                    10 /*pick one unused pin from network, e.g., */);
    return 0;
}

[Benno Trutmann]

Hi Vidar.

Indeed mapping the net-cpu LED signal to an unused pin fixed the problem with TX_EN.

Thanks,
Benno