Serial & reset of the device
invalid at invalid.invalid
Fri Jul 8 15:56:12 CEST 2011
On 2011-07-08, Tim Chase <python.list at tim.thechases.com> wrote:
> On 07/08/2011 02:45 AM, Tim Roberts wrote:
>> yorick<yorick.brunet at gmail.com> wrote:
>>> I'm trying to access a hardware board of my company through a serial
>>> connection using a Python script and the pyserial module.
>>> The board to which I'm trying to connect works correctly with serial
>>> as some other guys did some TCL scripts to manage it. My problem is
>>> that every time I open a new connection, the device is reset. I'd
>>> like to not have the device reset.
>> I'm not sure what that means. The RS-232 standard does not have the
>> concept of "reset". What is it that triggers a device reset?
> While not a "reset" per-se, it might be triggered by the RTS/CTS,
> DSR/DTR, or carrier-detect pins depending on the configuration.
> Without the code and with minimal pySerial experience, I don't
> know whether opening a serial-port in pySerial automatically
> lights up one of those aux. lines and unsignals it when the
> connection is closed.
On Unix, the serial port device driver generally turns DTR and RTS off
when a port is closed and turns them on when it's opened. I don't
know what Windows does. A quick glance through the pyserial sources
shows that it turns on DTR and RTS when a port is opened, and does
nothing with them when a port is closed.
If you need RTS/DTR to stay in a known state, then open the port, set
them to the state you want them, and keep the port open.
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