Question on SPI connection of RA8875 + Sd Card

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pmh
 
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Question on SPI connection of RA8875 + Sd Card

Post by pmh »

Try to get those parts working together: Arduino Due, Micro SD-Card breakout reader, RA8875 Touch Display Driver Board and 5.0" 40-pin 800x480 TFT Display without Touchscreen all from Adafruit
I am using the example ra8875_bitmap_fast. Since Arduino Due is supporting only the SPI interface and only Chip Select on digital 4, 10 and 52 I modified the SPI settings accordingly.
The sketch runs and on the serial monitor I read:
initialization done.
RA8875 start
Found RA8875
(800, 480)

Loading image 'parrot.bmp'
File size:
61496
Image Offset: 54
Header size: 40
Bit Depth: 24
Image size: 128x160
Loaded in 1368 ms

The TFT gives a very brief flash but no picture.
I read an old blog “The RA8875 does not tri-state the MISO pin, it should not share that pin with any other SPI device (including an SD card reader) without the use of a 74HC125 or similar”
Is it still valid for RA8875 bought in July 2021? If yes please tell me where to find the pinout/schematic diagram for this. I want to connect a third module (a DAB shield from dabshield.com) afterwhile. Thanks Michael
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pmh
 
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Joined: Thu Aug 05, 2021 10:30 am

Re: Question on SPI connection of RA8875 + Sd Card

Post by pmh »

Hello,
some hints in case anybody has the same problem:
- Check first the connections, I had problems with cheap cable connectors
- You will need an addtional power supply as the Arduino Due does not provide enough current to RA8875 + TFT. Don't forget to connect both ground together. Please not that I suplly the power for Due thrue the USB connector.
- After those things were fixed both sketch to display Text and Bitmap work well
- But I add a DAB Shield to the project and the communication thrue SPI does not work. I am investigating further.

--> Does anybody had to tri-state the MISO pin? As it was told in this forum a few year ago. If yes could you please share your experince and told us how you did it?
Chears

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