- Tue Jan 24, 2023 3:22 pm
#95879
I observed on my Witty Cloud board that data transmitted via TXD0 affects the level of RXD0.
In attached screenshots, yellow is the incoming data @ RXD0, blue is @ TXD0. The transmission speed is 2400 bps and toggled on/off for demonstration.
You can clearly see that RXD0 does no longer reach low level if transmission is active. Incoming data is therefore unreadable.
The other images show RXD0 with 10k pull up and 10k pull down resistor:
In case of pull-up, the impact on the level of RXD0 is clearly visible.
In case of pull-down, RXD0 does NOT reach GND.
What is the reason for this behaviour and how can it be avoided?
RXD0 pulled up to 3.3V by 10k (no external signal)
RXD0 pulled down by 10k (no external signal)
Impact of transmission on RXD0 (external signal connected to RXD0)
In attached screenshots, yellow is the incoming data @ RXD0, blue is @ TXD0. The transmission speed is 2400 bps and toggled on/off for demonstration.
You can clearly see that RXD0 does no longer reach low level if transmission is active. Incoming data is therefore unreadable.
The other images show RXD0 with 10k pull up and 10k pull down resistor:
In case of pull-up, the impact on the level of RXD0 is clearly visible.
In case of pull-down, RXD0 does NOT reach GND.
What is the reason for this behaviour and how can it be avoided?
