The goal is to design thermostat system via stacking Raspberry pi HATs:
- Raspberry pi (3B+ or 4)
- 4-channel relay
- TFT Touch Display
It would be preferable that community experience point out any obstacles before I purchase the relay-HAT and steer away from a poor design decision. Below is a preliminary analysis, however, I would like the community's experience to review and pick it apart for any obstacles.
DISPLAY: ======= PIN GPIO 11 17 TP_IRQ Touch Panel interrupt, low level while the Touch Panel detects touching 18 24 LCD_RS Instruction/Data Register selection 19 10 LCD_SI / TP_SI SPI data input of LCD/Touch Panel 21 9 TP_SO SPI data output of Touch Panel 22 25 RST Reset 23 11 LCD_SCK / TP_SCK SPI clock of LCD/Touch Panel 24 8 LCD_CS LCD chip selection, low active 26 7 TP_CS Touch Panel chip selection, low active
The DockerPi 4 Channel Relay display indicates I2C relay control. Given that the display uses the GPIO & PINS listed above.
- I2C pins in BCM mode are: 2, 3
- I2C pins in WiringPi are: 8, 9
- Can the two hats stack and perform their respective functions?
- Or is there a feature that I have not considered that may be an obstacle?
If you have had success stacking multiple HATs, please indicate which HATs and any lessons-learned in your reply.
UPDATE: Fail-safe \ failure-mode
Because the application is HVAC (heating , air-conditioning), it is important to understand failsafe modes and ensure that relays are not engaged in a failure mode