Using neopixel for external led lights

I would like to use neopixel to control an external led array using one of the AUX outputs. I’m using CUAV v5+ and PX4 version v1.12.3. So far I have been able to compile with the neopixel driver and I’ve set up the DMA configuration as follows in board_config.h:

#if defined(USE_S_RGB_LED_DMA)
#  define S_RGB_LED_DMA             DMAMAP_TIM1_CH1_2 
#  define S_RGB_LED_TIMER                1   /* timer 1    */
#  define S_RGB_LED_CHANNEL              1   /* channel 1  */
#  define S_RGB_LED_CHANNELN             1   /* channel 2N */
#  define S_RGB_LED_TIM_GPIO            GPIO_TIM1_CH1OUT_2

According to the documentation of the FMU v5+ the TIM1_CH1OUT_2 should correspond to FMU_CH4 (AUX4).
However when starting neopixel via mavlink shell I dont see anything happening on either AUX output, they all are at static 3.3V.
Does anyone know how to setup neopixel to use an AUX pin?