hilscher NIOT-E-TPI51-EN-RE User Manual page 129

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Edge Gateway | NIOT-E-TPI51-EN-RE (Connect)
DOC170502UM07EN | Revision 7 | English | 2019-07 | Released | Public
Timing behavior of the RS-485 interface in the context of switching
between transmit and receive mode
Switching between transmit and receive mode of the RS-485 interface of
the module NIOT-E-NPIX-RS485 is accomplished by a GPIO signal (GPIO
17, State High in send mode and Low in receive mode. Controlling GPIO
17 is done all in software causing a jitter.
Measurements using an oscilloscope have shown that the signal GPIO 17
is set to high state between 400 µsec and 1ms before the data is
transmitted. It falls back to low state 5ms to 32ms after the last bit has been
shifted out of the transmit shift register. Consider, that the module is able to
receive data again only after that time has passed.
Fast devices (<32ms) sending back data over RS-486 in a request/
response manner might not work with the RS-485 nodes.
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