Hello world :-) I am working on a pretty industrial automation project right now that will control 3 phase motor over 400V/25A relays.
There are 6 relays to provide all possible modes of 3 phase motor control. There are 3 groups of two relays for a task like direction change, star-left-star-right, and star-triangle switch. Each two of the relays in the group will have exclusive control (i.e. when one is on the other will have control cut off). But there groups are not fully exclusive physically due to their function. So when all three groups are turned on then big bang happens :-) I am still wondering how to protect against this big bang. For sure I will add some physical protection so this situation is impossible (i.e. some sort of logic between GPIO and relays where only one line will indicate possible safe operation state of all relays, while zero or more than one line set high will always result in a safe state). This lead me to think of the initial state of the ESP32 GPIO pins after boot then after NuttX starts.. or when device will be in bootloader / flashing state.. in case of malfunction.. or malicious actions (it might be connected to the internet somehow).. or simply sending 0xFFFF to /dev/gpio0 etc etc? My question is: it is possible to be sure of the GPIO pin state since power-on through bootloader + RTOS up to the application run? For instance not to let all pins go high/low/random? Any hints welcome :-) Tomek -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
