I'm thinking to connect about 50 slave Arduinos on 1 master using TX/RX. I'm following recommendation of these links:
- I'm looking for a way to serially communicate with a multi mesh Arduino slave network, and;
- Tx/Rx UART communication between 2 MCU over 1 line
using the cathode of diode connected to slaves TX pins and pulling up this line, like this image:
In Arduino - Digital Pins, when pin is set to input (high impedance), it is "equivalent to a series resistor of 100 MΩ in front of the pin". Slave RX line has input (RX pin) in parallel, then, if this 'equivalent resistor' is true, we have a low resistance (duo parallel configuration) that burn the master TX. Is it make sense?
I have not found either in the Arduino or the ATmega documentation, if TX port have the internal pullup on. In ATmega documentation, TX pin is set as output and RX pin as input. The TTL logic is high on idle, then 5 V must be sourced from somewhere, correct?