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Thread: PWM Control of Brightness for TI TPS61165

  1. #1
    Junior Member
    Join Date
    Jan 2021
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    PWM Control of Brightness for TI TPS61165

    I have a Newhaven display that uses a TI TPS61165 driver (https://www.newhavendisplay.com/user....0-HDMI-HR.pdf). I am trying to control the brightness with a teensy 3.2. According to the documentation for the TPS61165 a PWM signal can be used to control the display brightness (https://www.ti.com/lit/ds/symlink/tps61165.pdf). The description of pwm control starts on page 12 of the datasheet. The PWM frequency should be between 5 and 100 kHz according to those docs.

    So far I have only been able to get the display to either be full brightness or not on at all. I've tried several frequencies and resolution settings with no difference in behavior. Here is the latest code that I've tried:

    Code:
    pinMode(DISPLAY_PWM_PIN, OUTPUT);
    
    analogWriteFrequency(DISPLAY_PWM_PIN, 35156.25f);
    analogWriteResolution(10);
    
    analogWrite(DISPLAY_PWM_PIN, 1024);
    DISPLAY_PWM_PIN is pin 5. This results in the display at full brightness, as soon as I call analogWrite with any value lower than 1024 (or lower than 256 when resolution set to 8) the display completely turns off. If I then call analogWrite with 1024 again the display comes back on at full brightness. This looks fairly straight forward so I'm not certain where I could be going wrong. Any ideas?

    For completeness the display is connected via HDMI to a raspberry pi 4. The full project code is c++ using platformio.

    Thanks!

  2. #2
    Junior Member
    Join Date
    Jan 2021
    Posts
    2
    I found a thread on the Newhaven display forums that seems to imply that this is an issue for arduino in general for some reason with these display:

    http://nhdforum.newhavendisplay.com/....html#msg22623

    Going to reach out to Newhaven to see if they have any direction.

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