This is the 485 circuit I designed.
After the power is turned on, the D/R pin is always high regardless of whether the MCU_D/R pin outputs a high level or a low level. What is the reason?
Yuri Posted on July 3, 2020
That's the problem of optocouplers. For the next 8.5CA, it is better to use 12CA.
Lars Posted on July 3, 2020
I changed the TTL end resistor 511 to 101, 485 end pull-up resistor, 102 to 103
, But this is not suitable for long-term operation of the microcontroller.
Janna Posted on July 3, 2020
The drive current is small and the optocoupler is not fully turned on, resulting in no change in level.
