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I am working on a Cyberdeck using a RPI 4B and witty 3v7 for power management and UPS. My peripherals are as follows, a 6.6Ah 3.7V LIION battery, a RTL-SDR, a 4 digit 7 Segment display, a Raspberry Pi 7" touchscreen display, a cpu/ram heatsink with fan, 2 USB-A extensions, 1 USB C extension for power, ethernet and a power switch. When I had first assembled this a week back, everything worked as intended. Now I have an issue where in most conditions, pressing the power switch will power on the Pi for a couple seconds, the screen never powers on and within 5 seconds the SD activity light goes out and immediately after the power is cut to the board. At first it seemed like the witty pi was dying so I ordered another for testing. The same problem occurs with a brand new 3V7. Using USB C power will allow the board to post, boot and run like normal. I tried powering the 3V7 directly from a power supply at 3.8V 3A, still nothing. I tested all connections for shorts or open circuits and found nothing. I put 5V 3A straight into the PI and it worked fine, powering the pi and all peripherals. It was using less than 1.5A so power is not the issue. Another case, with all peripherals disconnected, the Pi will run off the battery alone. I slowly started disassembling to see at what point it would power on, that happened to be when the Screen control board was disconnected. I check that board and swapped it for one I knew works, nada. At this point I am out of ideas, I think it may be a software issue as I have burned myself out checking hardware. I would do a clean reinstall of the OS but I spent too long getting softwares installed and would like that as a last ditch effort. I may try a brand new SD with a clean install.
Any help would be greatly appreciated.
Posted : 06/12/2024 5:12 am
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I tried reinstalling the wittypi software and a fresh OS, neither worked. I should have said, I2C and Serial are enabled and 1-wire is disabled. The gpio readall looks good, and all other troubleshooting tips in the manual bared no fruit
Posted : 06/12/2024 6:14 am
@g-berta What is your Witty Pi 4 L3V7's firmware revison?
It is printted in the wittyPi.log file.
Posted : 06/12/2024 10:46 am
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@admin It is firmware ID 0x37 and Revision 0x07. I can send the whole log file if that helps.
Posted : 06/12/2024 10:19 pm
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@admin I measured and GPIO 23 (BCM) is always low. Also, when the RPi screen is powered separately (bench power supply) the whole system works as intended. So I believe there is some conflict between the RPi screen and the 3V7. I still find this very odd as it worked for multiple weeks with the screen powered through the Pi's 5V out
Posted : 06/12/2024 11:03 pm
@g-berta although you measured the pi and all peripherals was using less than 1.5A, that could be a "smoothed" value and the actual peak value could be (much) bigger.
Your 3.8V/3A power supply can only give about 2A current on 5V, that is really not much.
Your battery, depends on its discharge C value, could deliver (much) higher current. But according to your description, it is possible that your battery's performance is dropping low: it can deliver enough peak current before, but it can not now.
If the power source can not deliver enough peak current, the input voltage will drop within very short moment, and the MCU may get reset, which also leads to power cut.
Posted : 07/12/2024 9:50 am
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@admin Running my PSU with 3.8V and 10A allowed current does not allow for the board to start up either. I am going to try a new RPi. I will update this thread if I come to a solution.
Posted : 08/12/2024 12:16 am