Add support for active high output enable #1377
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This change added support for active high output signal for OE. Polarity of OE is control by output_polarity field in HardwareMapping. Signed-off-by: Khoa Hoang <[email protected]>
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This change added support for active high output signal for OE and also bring in support for my custom LED matrix cube hat name
cubie-hat. The output enable pin on this hat is inverted to avoid glitch on initial power on.Background:
The 3.3v power rail on Raspberry Pi 4 comes on later than the 5v input supply and since the OE is pulled up to the 3.3v rail on the active3 hat, there will be a short glitch on the OE signal at powering up causing unwanted flicker on the LED panel. To fix this issue, I added an NPN transistor to drive the OE signal on my custom hat and that fixed the issue.