Hi Everyone,
We're running Teensyduino V1.27 & Arduino 1.6.5-r5 on Teensy 3.1's. We're using the FastLED library to configure a large array of WS2812B (NeoPixel) LEDs. We're using 74HCT245 to convert the data to 5V before sending to the WS2812B pixels. We're consistently seeing a flash of random LEDs when we turn on the system, and looking at it on a logic analyzer (capture attached), we can see that there's a bunch of garbage data being sent to the LEDs on turn-on. We only see this problem when we turn on power to the system. If we upload new code and thereby reset the Teensy, we never see this problem. We have a lot of capacitance in the system to deal with power fluctuations from so many LEDs in our system, and we have ample power coming into the system from the power supply and 5V DC-DC converter. The 5V power rail is clean coming up, as seen by the attached scope capture.
So we're at a loss as to what could be different between powering up, and resetting the system. We looked into changing the LVDSC1 to use LVDH (2.56V) instead of LVDL (1.60V), but it doesn't seem like this would do anything for us, since the garbage data is happening over 100ms from the time that the Teensy powers up.
Anyone out there have any ideas on what this could be? Or a work-around?
Thanks and best regards,
Kent
We're running Teensyduino V1.27 & Arduino 1.6.5-r5 on Teensy 3.1's. We're using the FastLED library to configure a large array of WS2812B (NeoPixel) LEDs. We're using 74HCT245 to convert the data to 5V before sending to the WS2812B pixels. We're consistently seeing a flash of random LEDs when we turn on the system, and looking at it on a logic analyzer (capture attached), we can see that there's a bunch of garbage data being sent to the LEDs on turn-on. We only see this problem when we turn on power to the system. If we upload new code and thereby reset the Teensy, we never see this problem. We have a lot of capacitance in the system to deal with power fluctuations from so many LEDs in our system, and we have ample power coming into the system from the power supply and 5V DC-DC converter. The 5V power rail is clean coming up, as seen by the attached scope capture.
So we're at a loss as to what could be different between powering up, and resetting the system. We looked into changing the LVDSC1 to use LVDH (2.56V) instead of LVDL (1.60V), but it doesn't seem like this would do anything for us, since the garbage data is happening over 100ms from the time that the Teensy powers up.
Anyone out there have any ideas on what this could be? Or a work-around?
Thanks and best regards,
Kent