I want to communicate between 2 uCs of the same type and operating at the same voltages using the UART peripheral.
The distance between the 2 micros is about 2 meters, both micros share the same common ground, each micro has it's own 5v power supply.
BAUD rate is 19.2kps
I can not use a MAX232 chip due to space and cost limitations.
I put in current limiting resistors and TVS diodes on each unit. I will chose a TVS with the lowest capacitance I can find. The working voltage of the TVS will be 5v, and the breakdown will be around 8v.
The Max current of my uC pin is ~25ma, the micro is running 5v.
I can do a straight calculation for R1,R3,R7,R7 based just on protection (8v-5v)/25ma = 120 ohms.
For R2,R4,R5,R6, I guess I can do something similar based on specs of the TVS diode.
But, I am not sure for the sake of UART functionality what range or resistance would be ok. Please let me know your thoughts.