Replicating PiTFT board

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dstahlke
 
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Joined: Sat Jul 26, 2014 10:01 pm

Replicating PiTFT board

Post by dstahlke »

I ordered the standalone resistive touch screen, along with the associated connector and breakout board (products 1774, 1773, and 1492) with the aim of replicating the PiTFT on a breadboard. All I get is a white screen! Does anyone have any troubleshooting tips? Here are some things I tried/noticed:

* The pinout of the TFT module and that of the "0.5mm pitch FPC adapter" breakout board are reverses from each other. So pin 1 goes to pin 50 and vice-versa. I've compensated for this when wiring it up.

* Since I'm on a breadboard, I've tried lowering the SPI clock rate to 1MHz.

* I don't have the parts for the reset circuitry used by the PiTFT, so I've wired the TFT reset pin to a GPIO on the Pi and set the corresponding option for the fbtft module. Also I tried manually resetting the TFT before booting the Pi.

* I hooked up LEDs to the breadboard then probed each pin of the 0.5mm pitch connector with a battery in order to ensure that all pins were soldered with no shorts.

* The PiTFT board works fine with my setup. Also, if I plug my TFT module into the PiTFT board, it works fine.

* I'm not messing with the touch panel for now.

Much thanks for any suggestions! By the way, the reason I'm doing this is that I need a board that fits nicely above the Model B+, with the mounting holes in alignment, and without the connectors pre-soldered. I'll be putting a custom board between the Pi and the display, and so need my own connectors to avoid too much extra height.

And, perhaps this is a long-shot, but any chance that Adafruit wants to open-source the CAD files for the PiTFT board?

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dstahlke
 
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Joined: Sat Jul 26, 2014 10:01 pm

Re: Replicating PiTFT board

Post by dstahlke »

I tried the python code from Adafruit's github repo Adafruit_Python_ILI9341, with the same results: the PiTFT works but my breadboard version doesn't.

Another question: the PiTFT schematics show 22 ohm resistors between the TFT and the Pi on the SCLK and MOSI lines. What is the point of this? Why only on these two lines? I have tried with and without these resistors, and also with resistors on all input lines.

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