Hi, KlausST,
Yes, you are right.
RXD etc. nets are linked to STM32 UART port.
And the nets with "R" prefix are converted by a IC, MAX3237, then linked to one laptop USB port with a USB/DB9 cable.
So I think the process is as following:
1. STM32 UART port output 5V TTL signal
2. 74LV4066D is one switch to switch the direction of the UART signals, because there are two directions, only one can be selected.
3. MAX3237EIDBR as relay or level compatible function, change 5V TTL to 3.3V or 5V??? to a DB9 serial port
4. Then by a link cable, link to the USB port of laptop.
I am a little confusion about the level convertion here.
Who can comment?
Thanks.
Tony Liu
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I understood a little:
MAX3237 converter TTL levels to a standard RS232.
Then I see.
Thanks.