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Testing a new display with touch capabilities.

A project log for ROENDI

Roendi (Rotary Encoder with Display) features a STM32L433 MCU, 1.28" TFT round display and a Alps Alpine 15Pulses/30Detent encoder.

dimitarDimitar 07/28/2022 at 11:530 Comments

Hey everyone!

Unfortunately we have been hit by the chip shortage as everyone else. Instead of waiting for things to blow over, we decided to do some research and development. 

Quite a lot of people asked for touch screen version of the RoEnDi.

Fortunately there is a capacitive touch version of our 1.28" round display. It requires more IOs and it is a bit bulkier than the regular one. My friend who does the mechanical stuff, will have a few things to figure out :D :D :D

I used one of the RoEnDi's test board to hook up the display and test it. The controller used is the CST816S, which is fairly popular with a lot of code examples.

A few things to note if want to play around with it:

1. You will need a 24 pin ZIF connector. Or mad ninja soldering skills, like on the phone repair videos you watch for hours. 

2. In my case I had to get a adaptor board for the 24 ZIF connector, because it is very fine pitch and I really wanted to skip the soldering of tiny wires part. 

3. The CST816S goes to sleep when there is no touch input. It is awake just after reset or after user input. This is done to save power which is nice. But to talk to it you either have to reset it or wait for the interrupt pin to signal that the devices is been used and then send messages on the I2C. 

More or less quite nice combo of display and touch panel. I will upload some code examples and PDFs for reference on my git hub page. 

PDFs: https://github.com/crowd-supply-projects/roendi/tree/main/references/Touch%20Controller

Code: https://github.com/MitkoDyakov/Roendi/tree/main/Software/STM32CubeDemo/DisplayWithTouch

Cheers everyone

Mitko


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