Number of neopixel leds not showing correctly

Dan_Moss · March 17, 2023, 3:46pm

Hi,
I would like to use a strip of LEDs (WS2812B) that are 55 leds long. but only the first 33 are illuminating.
I am controlling with the examples/LED_roll.lua , swapping to use set_num_neopixel, and adjusting the num_leds. if i set num_leds to anything less than 33 it shows that many as expected but over 33 no more appear. ive also lowered the brightness by halving all the values in the rainbow func so shouldnt be near the current limit.

I’m using rover 4.3.0-beta10 on a H743-SLIM. connected to servo9 in pwm group 4 (as the only thing in that group)
paramsLED.param (18.6 KB)
.

the leds also change on the here2 gps to off once the battery is plugged in (unsure if related)

Yuri_Rage · March 17, 2023, 4:55pm

That’s an awful lot of LEDs if you are sourcing power from a pin on the autopilot itself. Recommend testing with a bench power supply to confirm if you are indeed running into a current/voltage drop issue.

As far as I know, the firmware limit for LEDs on a single channel is 128.

Dan_Moss · March 17, 2023, 6:39pm

If that was the case of the overload, why would turning down the brightness not help illuminate more than 33?
If it’s high or low it’s always 33

Yuri_Rage · March 17, 2023, 6:40pm

Could be voltage drop in the data line or a bad pixel as well.

rishabsingh3003 · March 17, 2023, 6:46pm

This is a known ArduPilot problem - Copter-4.2.0 - Possible problem found that doesn't make the leds work normally (DShot) (luminousbees) · Issue #20816 · ArduPilot/ardupilot · GitHub

Dan_Moss · March 17, 2023, 6:54pm

Thanks Rishabh, if I’m not using dshot is there a way to overcome this?

Yuri_Rage · March 17, 2023, 6:59pm

I didn’t realize there was a fundamental issue - great pointout!

You could split the LEDs across multiple channels or use an intermediate device like an Arduino and connect as many lights as it will suffer. But if you read the entirety of that issue, there is no resolution for single channel LEDs.

Dan_Moss · March 17, 2023, 8:18pm

i made a build with the max ms *2 as per this line:

github.com

ArduPilot/ardupilot/blob/32578b796bc360520306d54540f4909c6af4986f/libraries/AP_HAL_ChibiOS/RCOutput.cpp#L255


      
                      }
                      if (pulse_elapsed_us < group.dshot_pulse_send_time_us) {
                          // better to let the burst write in progress complete rather than cancelling mid way through
                          wait_us = MAX(wait_us, group.dshot_pulse_send_time_us - pulse_elapsed_us);
                      }
          
          
            // waiting for a very short period of time can cause a
                      // timer wrap with ChibiOS timers. Use CH_CFG_ST_TIMEDELTA
                      // as minimum. Don't allow for a very long delay (over _dshot_period_us)
                      // to prevent bugs in handling timer wrap
                      const uint32_t max_delay_us = _dshot_period_us;
                      const uint32_t min_delay_us = 10; // matches our CH_CFG_ST_TIMEDELTA
                      wait_us = constrain_uint32(wait_us, min_delay_us, max_delay_us);
                      mask = chEvtWaitOneTimeout(group.dshot_event_mask, chTimeUS2I(wait_us));
          
          
            // no time left cancel and restart
                      if (!mask) {
                          dma_cancel(group);
                      }
                      group.dshot_waiter = nullptr;
          #ifdef HAL_WITH_BIDIR_DSHOT

and now all the LEDs work