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S-March / smarchWatch_Public

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Something interesting in Schematic file #34

Open ValentiWorkLearning opened 5 years ago

ValentiWorkLearning commented 5 years ago

In Schematic file I noticed, that display's WR pin has't any connections on board and display driver uses the 9-bit SPI for transfering data between display and MCU. In ST7789V datasheet I've found that WR pin uses for selecting, what would be transfered - command or data. So, Why do you use the 9-bit SPI for display communication and where you find information about the display's interface? image I've created this issue because have a similar display, but haven't got any succesful results because trying to use 8 bit SPI with selecting data and comannd with toggling the WR pin. Thanks for answer!

S-March commented 5 years ago

Hi there!

I actually ended up using 9-bit SPI because I spent two weeks trying to get the display to work with the Data/Command line toggle and it wasn't working. I was banging my head against the wall and after pouring over the datasheet for the driver, noticed it had the option to do 9-bit SPI. The display would pick either 3 wire SPI, 4 wire SPI, a parallel approach or use of the Data/Command lines depending on how some internal (to the display) hardware bits were set. I had been looking at the data packets on my logic analyzer and couldn't find anything wrong with what I was doing.

Since I had nothing to lose, I tried the 9-bit approach and voila! The initialization code I had ran and my display turned on.

The only way I figured it out was by dumb luck. There was no documentation for it anywhere.

Page 33 of this datasheet talks about the selection of the communication mode and then page 63 talks about how to pack the data.

Hope that helps!

ValentiWorkLearning commented 5 years ago

Thanks a lot for your answer! Therefore, interface with 3 and 4 wires is true random that defined only by display vendor. I'll try one more with 9-bit SPI. Think, it must be successful. Thank you! It will be nice, if I could contact with you on Facebook/etc, if possible.

ValentiWorkLearning commented 5 years ago

Please, may you attach the waveform from logic analyser for init sequence?