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.
A touch-display hat was purchased from Amazon.com: based on the pinout data from the waveshare website the display uses:
DISPLAY:
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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
QUESTIONS
- 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?
BONUS ROUND
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
