The comments in serialport.c indicate an intention to leave the serial
port control lines untouched during sigrok opertion; the code then
mixes-in a HUPCL flag to the termios bits that will be set on the serial
port.
The effect of setting a HUPCL bit is that modem control lines will be
asserted when the last user of the serial port closes its open handles.
So the net effect of setting this bit is that sigrok effects a hangup on
close. For FTDI usb-serial expanders this is state change of the DTR
pin.
For boards like the buspirate, this is not an issue when using the OLS
driver -- the bus pirate does not make use of the DTR pin on the FTDI
serial expander; however, boards like arduinos and the JTAGulator do.
They use it for programming purposes but the result in spurious DTR
state changes is a reset of the processor. The latter of these two
is having a OLS compatibility layer added.
So, when using the OLS driver with this in-development JTAGulator
firmware, a reset occurs on close of sigrok-cli and on completion of
capture in pulseview. This is a problem for systems like the jtagulator
which do not persists any configuration -- critically, voltage settings.
Please consider this patch for inclusion; based on my understanding of
the HUPCL bit the changes here correct code to match the intent stated
in the code comments.
Signed-off-by: Ben Gardiner <ben.l.gardi...@gmail.com>
---
I have tested this with the OLS driver (and a WIP JTAGulator firmware)
on a Linux host -- as well as with the same platform and driver against a
bus pireate; however, the serialcomm transport is used by many more
drivers than OLS. I'm not sure this is a valid change for all of them
but I expect it would be (which is why I'm submitted this patch). My
expectation here could be wrong if any of the devices whose drivers use
the serialcomm transport rely on DTR toggling on close.
---
serialport.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/serialport.c b/serialport.c
index d271478..bd63643 100644
--- a/serialport.c
+++ b/serialport.c
@@ -586,7 +586,8 @@ SP_API enum sp_return sp_open(struct sp_port *port, enum
sp_mode flags)
data.term.c_cc[VTIME] = 0;
/* Ignore modem status lines; enable receiver; leave control lines
alone on close. */
- data.term.c_cflag |= (CLOCAL | CREAD | HUPCL);
+ data.term.c_cflag |= (CLOCAL | CREAD);
+ data.term.c_cflag &= ~(HUPCL);
#endif
#ifdef _WIN32
--
2.6.1.134.g4b1fd35
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