Arch Linux

cyber-marble

Member

Registered: 2017-08-27

Posts: 3

stty provides no way of turning on DTR DSR handshaking

Hello,
the stty that ships with Arch Linux (?) provides no way of turning on DTR DSR handshaking.

stty --help | grep -i dtr

gives no result.
Is there an other tool/package that provides this feature?

regards,
marble

Last edited by cyber-marble (2017-08-28 10:24:45)

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: stty provides no way of turning on DTR DSR handshaking

Last time I checked it wasn't implemented in the kernel. If DTR/DSR protocol is compatible with RTS/CTS (and IIRC they are identical) it should be possible to build an adapter cable which connects your device's DTR/DSR to the Linux machine's RTS/CTS. Then crtscts enables RTS/CTS flow control.

cyber-marble

Member

Registered: 2017-08-27

Posts: 3

Re: stty provides no way of turning on DTR DSR handshaking

Oh darn

Ok, I also thought about this "cable hack" but clinged to the idea of integer RS232 cables.
But yeah. that's definitively an option...

cyber-marble

Member

Registered: 2017-08-27

Posts: 3

Re: stty provides no way of turning on DTR DSR handshaking

Odd enough is that pyserial is capable of reading the DTR line. Doesn't this conflict with
"Last time I checked it wasn't implemented in the kernel."
?

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: stty provides no way of turning on DTR DSR handshaking

The kernel knows about DTR/DSR pins and supports reading/writing them. But it doesn't have a concept of hardware flow control on these pins: there is no API to request DTR/DSR handshaking and no support in hardware drivers to program the UART chip to perform it (hardware flow control is performed by the hardware, duh). Only RTS/CTS is supported. Yes, it's a stupid and unnecessary limitation but apparently nobody cared enough to fix it.

BTW, you don't need to do any ugly cable splicing, you can buy male and female DB9 connectors and build a neat adapter if you want it to look good

Last edited by mich41 (2017-08-28 21:18:00)