Hardware SPI sharing for two devices on Arduino Due

Hardware Arduino Due
1

I have a sensor and arduino TFT display sharing the hardware SPI on arduino due. In presence of the MISO of Arduino TFT, the sensor is unable to use the MISO line. As soon as I detach the MISO of TFT, the sensor is able to use the MISO again. I have gone through the information about Hardware SPI sharing for two devices on Arduino Due. But Im unable to figure out why this is happening. I have even tried setting HIGH the CS pin of TFT at the time SPI tranfers are being carried out by the sensor. Even that isn't working... Any useful information or solution will be greatly appreciated.

2

https://www.dorkbotpdx.org/blog/paul/better_spi_bus_design_in_3_steps

3

Maybe the display has a RA8875 controller?

RA8875 does not tri-state its MISO pin when its CS is high.

4

Thanks for the valuable inputs.

The display I'm using is this and it uses the the Adafruit GFX, and Adafruit ST7735 libraries. May be I should try some other display device that works smoothly in sharing the SPI with the sensor.

5

From the schematic, looks like Arduino designed this shield with a 74LVC1G125 buffer chip that is always enabled. The display is ok, but this added buffer chip is always driving MISO. :frowning:

You could probably make this work by cutting the trace to pin 1 of IC3 and instead connect it to the LCD_CSB signal (pin 4 of IC1).