Differences

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--- doc:appunti:hardware:serial_timedia [2012/06/27 16:33] – niccolo
+++ doc:appunti:hardware:serial_timedia [2012/09/25 17:19] (current) – niccolo
@@ Line 31: / Line 31: @@
 : uart:16550A port:0000A808 irq:177 tx:0 rx:0
 : uart:unknown port:000002E8 irq:3
+</code>
+===== stty hangs while reading the device =====
+Here's a problem with the old redirection operator (which doesn't happen if you use the newer -F option instead). Sometimes when trying to use stty, the command hangs and nothing happens (you don't get a prompt for a next command even after hitting <return>). This is likely due to the port being stuck because it's waiting for one of the modem control lines to be asserted. For example, unless you've set "clocal" to ignore modem control lines, then if no CD signal is asserted the port will not open and stty will not work for it (unless you use the newer -F option). A similar situation seems to exist for hardware flow control. If the cable for the port doesn't even have a conductor for the pin that needs to be asserted then there is no easy way to stop the hang.
+<code>
+stty --file=/dev/ttyS4 clocal 9600
+stty --file=/dev/ttyS5 clocal 9600
+</code>
+In Ubuntu see this [[https://bugs.launchpad.net/ubuntu/+source/modemmanager/+bug/490194|bug 490194]]: modemmanger is too aggressive with serial devices, it runs after ''/etc/rc.local'', so the best bet is:
+<code>
+dpkg --purge modemmanager
 </code>