Hi, I’ve built a rPi 4B-based player, power filter hat, DAC hat, and 7" touchscreen. During testing, it booted up and played fine without the touchscreen while waiting for the right cabling. With the touchscreen connected, however, the Pi is in a continual boot loop.
I’ve tried using a 2nd USB power adapter into the touchscreen’s 2nd micro USB port. And I’m assuming the DC power input to the filter is 5V around 1A along the lines of USB power, though this is unspecified. I’ve reached out to the seller to find out.
You might also have a conflict in what GPIO pins they are using.
This site is useful to see what pins are used by a wide variety of HATs.
But if you just put the touchscreen on, does it boot? Then add one or other of the remainder, then swap them and see if there are two items that are incompatible, or if you’re just overloading things power-wise with all three.
Did you try booting the Pi also with a standard PiOS install?
That might give more clues, as if power is low it boots but with a lightning bolt symbol for example (unless it’s hugely overloaded).
Good ideas - thx. I had some busy time during a meeting and built it up attached to the back of the screen with standoffs, etc. before testing, even though I know better. I suppose I should pull it all apart instead of guessing at the issues.
Does your 7" touch screen have a power connection jumper back to the Pi and a power select switch. Unless you disable this you will still be drawing power from the Pi. Look at how many Amps your power supply puts out, this is critical if you want to power a hat attached to the Pi. There is a big difference in quality and output of all the different Pi power supplies. I am not an electrical engineer but you should also look into and see if a common ground is required using multiple power supplies.
This particular touchscreen does not have the switch. But I took your advice anyway, and used a high-current dual output brick with the second output into the touchscreen. It’s all been working for weeks. Thanks for that.
Now if I could just get the aspect ratio worked out. It looks stretched on the horizontal. I know that means tweaking a config file on the microSD but I skipped installing a microSD extender; it’ll be a while before I pull it, disassemble it, and experiment.
Not sure what the aspect ratio or the resolution of your screen is but you will probably have edit the config.txt.
Modify /boot/config.txt I had to make these changes: