neopixels on the nRF52840

Hey Robin, it's alright I think I got it working. Thanks for bringing up the topic, otherwise I would have just given up. I even used your [055,055,055, 055,055,055, 055,055,055, 055,055,055] test (which lights up all pixels white btw, no green led for me).

@Gordon it looks like LRCK is required to be defined, aside from SCK. I found a discussion on the nordic forums here: https://devzone.nordicsemi.com/f/nordic-­q-a/55802/driving-ws2812b-neopixels-with­-i2s-without-sck-lrck

Doing something like:

@@ -45,7 +45,7 @@ ret_code_t i2s_ws2812b_drive_xfer(rgb_led_t *led_array, uint16_t num_leds, uint8
 [#else](http://forum.espruino.com/search­/?q=%23else)
        config.sck_pin      = 22;
 [#endif](http://forum.espruino.com/searc­h/?q=%23endif)
-       config.lrck_pin     = NRF_DRV_I2S_PIN_NOT_USED;
+       config.lrck_pin     = 23;
        config.mck_pin      = NRF_DRV_I2S_PIN_NOT_USED;
        config.sdout_pin    = drive_pin;
        config.sdin_pin     = NRF_DRV_I2S_PIN_NOT_USED;

gets everything working.

I haven't tested and compiled with the nRF52832 boards with LRCK defined though, so I'm not sure if that would affect any of the functionality of the official boards.

Edit: the forum seems to mess up the diff, so here's a screenshot

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