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fix

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Wolfgang Hottgenroth
2019-06-18 19:06:59 +02:00
parent fcefd538d8
commit d19bc80783
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readme.md
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@ -120,7 +120,7 @@ But sometimes is does not work:
![Modbus comm not ok](./docs/modbus-not-ok.png)
The long hold time of the DE (transmitter enable, RTS line) becomes a problem, the response of the device already starts when the transmitter of the master is still enabled and thus the receiver of the master is still disabled.
The long hold time of about 18ms of the DE (transmitter enable, RTS line) becomes a problem, the response of the device already starts when the transmitter of the master is still enabled and thus the receiver of the master is still disabled.
A couple of experiments with deriving from the `RS485` class of `pyserial` and moving the time critical code (disabling the transmitter after the transmit) into C code failed. It wasn't faster at all. It became obvious that the system call `tcdrain`, which waits for all octets in the buffer to be transmitted returns very late.