Automation pHAT issues (breaking other HATs)



I have an automation pHAT, connectedit to a Pi Zero W using the mini Black Hat hack3r, along with a piTFT.

All was fine for a couple of days, then powering it up one morning, the TFT gives out noise. Removing the Automation pHAT solves the problem.

I have checked the GPIOs and there are no clashes. So:
Automation : I2C + GPIO[5, 6, 12, 16, 20, 21, 37]
TFT : SPI + GPIO[7, 8, 18, 24, 25,]

Apart from breaking out the SPI to a pin header, what could cause the automation pHAT to confict with the TFT?


as seen here the screen uses bcm18 for backlight control.

Unless you completely disable the on-board audio of the Pi, I would expect trouble… that said I don’t have one of these screens to test.


which I have just realised does not answer your question - but AFAICT, no, Automation HAT shouldn’t screw things up, unless the pinout documented is incomplete or the noise is due electrical interference of some sort.


Thanks for the response. As I first stated, I checked there were no clashes before I purchased both.

It also, worked correctly for a couple of days and then made the screen go funky. So, I assume there is some undocumented features that cause issues after a while. But since I dont’s have circuit diagrams for both, I can not check…


How have you connected the 2 add-ons? … the TFT requires the HAT EEPROM i2c lines to be connected (phys pin 27-28). As per HAT specs, this means that Automation HAT should on the other hand not be connected to these lines, or the TFT auto-configuration will not happen correctly at boot time.


As stated in my first post, I am using the mini Black Hat hack3r. I believed, as it was I2C, they would be fine, afterall, that IS what the Black hat is for, is it not!

If that is not the case, how DO people connect multiple hats/shields?


again, you MUST disconnect phys 27-28 for one of the HAT, it will simply not work otherwise if one of them is relying on auto-configuration on boot (see the ‘EEPROM’ description on the TFT at

One way to do that would be to snip those on one of the header on the mini Black HAT. Alternatively, use a full set of wires to connect exactly the needed connections for one of the HAT.


OK. Will give it a go.