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bacnet-stack / bacnet-stack

BACnet Protocol Stack library provides a BACnet application layer, network layer and media access (MAC) layer communications services.
http://bacnet.sourceforge.net/
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Manually setting the RTS pin for RS-485 #119

Open kmare opened 4 years ago

kmare commented 4 years ago

First of all, thank you for this library, great work :) I'm trying to to communicate with a BMT-DO4. This is working fine when using an USB RS-485 dongle. But as soon as I try to use the native RS-485 port instead of the USB dongle, the communication fails (sending a bind request, but can never bind until it timeouts). My understanding is that I would need to manually set the RTS pin high and low depending on when I'm transmitting or receiving a frame. Where would be the best place to add such a change? As far as I know/understand, libmodbus did something similar as it can be seen here: https://github.com/stephane/libmodbus/blob/master/src/modbus-rtu.c

skarg commented 4 years ago

For the Linux version of RS485, the RTS pin would need to be toggled in ports/linux/rs485.c in the RS485_Send_Frame() function before and after the write() call. For the Windows version of RS485, the RTS pin would need to be toggled in ports/win32/rs485.c in the RS485_Send_Frame() function before and after the WriteFile() call.

parthEmbedded commented 3 years ago

Do you need to add delay before or after toggle?