Could you help me debug a touchscreen problem please?
I got the touchscreen at least a year ago, and got it working OK. Then I put it away and didn't touch it for the longest time.
Now I have a use for it, I'm having a big problem getting it working. I initially tried powering it using the GPIO pins, which were definitely connected correctly. (I've done a lot of GPIO stuff, a trivial mistake there is not the problem. I'm not saying there may not be a careless mistake somewhere, just that that particular one is not it. I've checked and double checked, and I've also removed the gpio wires and tried with two separate USB supplies. Still no dice. One of the power supplies is an Apple one which I tested with a USB amp/volt meter and a dummy load and it is capable of supplying 2.65A so I am confident we have good power.)
There's no indication it is powering up at all. Not a grey screen or anything, it just looks dead. If I connect an HDMI to the Pi, it comes up. There's no indicator on the HDMI display that there's a lack of power. I'm using my best USB power supply (one of the ones from Western Digital that usually powers a Pi with a Pidrive attached) No peripherals attached - I did have a USB mouse and keyboard on it but I removed them to keep it simple as soon as I was booting and had a network connection.
dmesg | grep -i ft5406
I also did the OS updates from the troubleshooting guide, and I tried a few more USB Power supplies.
I've also carefully removed and reinserted the ribbon cable and made sure it is the right way round. (And it is in the display port, not the camera port
There aren't any lights or switches on the touchscreen's board are there? Even when I power it directly with a USB supply it remains completely black. Not a single indication of life. Here's an interesting clue
: I just now put a USB power meter in circuit with the USB supply feeding the display. 0.00 amps! Even when I power up the Pi, no change on the display. The display is not drawing any power
This is a new Pi3 and I've installed Raspbian from the Noobs 1.9.2 off the Raspberry Pi Geek CD. It boots up into Pixel so I know for sure it's a very recent version.
What could I have missed? Unfortunately I no longer have the SD from last year when it worked or I would have tried that first.
After trying all the above, I even removed the display board from the LCD panel and removed and reinserted the two cables that connect the logic board to the screen, just in case they had somehow come loose. (though unlikely as I received the board already assembled).
These do work with Pi3's, right?
Any advice on how to debug this welcome. By this point I would be suspicious of a dead board if it weren't for the fact that it was working when I put it away and it has been well protected in its original foam-padded box since I last used it - albeit over a year ago.