Serial communication

QWE4562009

Serial communication [Copy link]

Serial communication


PCBA1 and PCBA2 are connected via serial communication. There are four wires, namely 4.2V from PCBA1 charging IC (to charge the lithium battery of PCBA2), GND, TX, and RX.

The application scenario is that sometimes the 4.2V output of the charger needs to be turned off, that is, not to charge the battery of PCBA2. If Q1 is turned off, then the S source of Q1, that is, the left side of Q1, should be 0V. (It seems that the battery voltage will pass through the body diode of Q1, so the voltage of the S pole is VBAT-0.3V?) If the body diode is not considered first. If Q1 is turned off, there is still a voltage of 2-3V at the S pole. At this time, do we need to consider whether it is caused by TX or RX? In a previous project, the mode of the TX or RX port was set incorrectly, resulting in a voltage being passed to the MCU of another board, such as open drain, multiplexed open drain output, push-pull, multiplexed push-pull output, analog input, floating input, pull-down input, pull-up input, etc.


How to guide the embedded system to set the correct serial port status in this case? What mode is it usually set to? Serial communication between two boards

wangerxian

You can try pull-down input or push-pull output low level.

QWE4562009

wangerxian posted on 2021-12-24 14:38 You can try pull-down input or push-pull output low level.

Do both MCUs do that?

wangerxian

QWE4562009 posted on 2021-12-31 19:22 Do both MCUs do that?

Yes, if possible, do this for both MCU's TX.