Comms Link hacking

[Daren]

I opened up one of my Comms Link with a view to fitting a wifi PCB inside, looks like there will just about be space to fit a Wenos D1 type ESP board. Anyway, I noticed a MAX232 level shifter on the pcb, which makes sense as it converts RS232 to TTL levels, which the top slot can tolerate.

I had initially planned on using a small MAX3232 board to interface the ESP to the comms link, but now I’m thinking I should be ok to connect to the MAX232 for the ESP RX and TX lines. I think the voltage from the MAX232 is 5v, but the ESP is probably 3.3v - so my question is would I be ok to just use some current limiting resistors (or actually a voltage divider) or am I better off modifying the circuit in some other way?

[amenjet]

I opened up one of my Comms Link with a view to fitting a wifi PCB inside, looks like there will just about be space to fit a Wenos D1 type ESP board. Anyway, I noticed a MAX232 level shifter on the pcb, which makes sense as it converts RS232 to TTL levels, which the top slot can tolerate.

I had initially planned on using a small MAX3232 board to interface the ESP to the comms link, but now I’m thinking I should be ok to connect to the MAX232 for the ESP RX and TX lines. I think the voltage from the MAX232 is 5v, but the ESP is probably 3.3v - so my question is would I be ok to just use some current limiting resistors (or actually a voltage divider) or am I better off modifying the circuit in some other way?

As TX and RX are uni-directional signals you should be OK dividing the output to 3V3 and applying the 3V3 directly to the input. Is it a 5V device? i think it has charge pumps and outputs about 7V or something doesn't it? Maybe not, it's been a while.