2.1 inch display SPI type

Projects General Guidance
1

Hi all.

I'm working on a project which uses this 2.1 inch circular TFT LCD display. It uses the ST7701s driver IC with an SPI interface for configuration and RGB666 for data. I'm having an issue getting it to work as I'm not 100% sure what kind of SPI is being used. The ST7701s supports 8-bit, 9-bit or 16-bit SPI from what I've read from its datasheet. I know that the display isn't using 8-bit SPI since there's no D/C (Data/Command) pin on the connector but whether its using 9-bit or 16-bit I'm not sure.

I'm hoping someone who has used this display previously can let me know what kind of SPI it uses as it seems to be the same configuration across multiple vendors of this kind of display.

Thanks in advance.

2

I think it doesn't have that pin because it only receives commands via SPI, it receives data via the parallel bus.

3

Well there's two different types of data here. Data on the SPI bus which goes into the ST7701s registers and data on the RGB666 bus which goes to the pixels.

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When there is no D/C pin, the D/C is specified through an extra bit in each SPI transmission giving you the 9-bit SPI configuration.

4

Found it through trial and error :), turns out it was 9-bit SPI. If anyone comes across this in future it is most likely 9-bit SPI if the connector is missing the D/C pin. Hope this helps :slight_smile:

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