Raspberry PI NRF24L01 gateway & WDT shield is fully compatible with Raspberry PI 3 Model B
This shield is compatible with NRF24L01+ and NRF24L01+ LNA radio modules and have hardware watch dog timer based on NE555 to use this option is required soldering of RUN connector on PI board, also soldering jumpers J1 and J2. Hardware watch dog timer is controlled via PIN 37 (GPIO26) if no signal more than 60 sek. reset pin goes low, and shield reset the raspberry pi. If a shorter time is required, then reduce the value of R1 or value of C1. Software for WDT not include have to be written by yourself, in my case I include cron execute directly to my controller.
Examples for WDT control software you can see on the link below: https://www.raspinews.com/blinking-led-on-raspberry-pi-using-python/
Example for OpenHAB rule driving Watch Dog Timer https://github.com/thetiana/WatchdogRuleForOpenHAB
Wiring of NRF24L01+ radio module is same as mysensors.org example and should work without any additional setup. To use information RX/TX/ERR LEDs must set parameters: --my-leds-err-pin=12 --my-leds-rx-pin=16 --my-leds-tx-pin=18
Watch dog timer not working for Raspberry PI 2 and Raspberry PI 1 Model B because of different position of RUN connector on the PI boards. But is possible to be used on those boards with soldering of additional wire to run connector on the raspberry pi.
Is possible additional shield to be stacked on the top this. Stacking have to be made with double stack long tail leg header. Be advise those pins are already used:
PIN 11 (GPIO17) - J3 PIN 5 dedicated for external relay
PIN 12 (GPIO18) - Error LED
PIN 13 (GPIO27) - J3 PIN 3 dedicated for external relay
PIN 15 (GPIO22) - NRF24L01+ IRQ
PIN 16 (GPIO23) - RX LED
PIN 18 (GPIO24) - TX LED
PIN 19 (GPIO10) - NRF24L01+ MOSI
PIN 21 (GPIO9) - NRF24L01+ MISO
PIN 22 (GPIO25) - NRF24L01+ CE
PIN 23 (GPIO11) - NRF24L01+ SCK
PIN 24 (GPIO8) - NRF24L01+ CSN/CS
PIN 29 (GPIO5) - J3 PIN 4
PIN 31 (GPIO6) - J3 PIN 6 dedicated for external relay
PIN 32 (GPIO12) - J3 PIN 7 dedicated for external relay
PIN 33 (GPIO13) - J3 PIN 8 dedicated for external relay
PIN 37 (GPIO26) - input signal for watch dog timer
Camera and display port are blocked by shield
J3 GND - PIN 1
J3 VCC - 3V3 PIN 2
Is possible J3 Pins dedicated for external relay to be used for input but resistors R10, R11, R12, R13, R14 must be replaced with 0R 1206 package.
C3 and C5 capacitors is for improve power stability when NRF24L01+ module transmit signals U1 is 3,3V voltage regulator for the NRF24L01+ modules and WDT mainly for NRF24L01+ LNA because Raspberry PI cannot supply enough power.
|Qty||Value||Device||Package||Parts||Description||MF||MPN||Aliexpress or Ebay link|
|2||2X4 Socket 2.75mm||Socket||J3|