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List: linux-hams
Subject: Re: RaspberryPI and soundmodem PTT
From: Ugo Poddine <ugop () libero ! it>
Date: 2014-12-05 14:44:48
Message-ID: loom.20141205T151705-771 () post ! gmane ! org
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Hi everybody,
There is also a different cheaper solution.
a) detach the serial console output from the UART pins of the gPIO board, as
described in several RasperryPI documentation (google can find) : basically
editing the /boot/cmdline.txt startup file...
b) modify, using a text editor (not the soundmodemconfig utility !), the
soundmodem.conf file, setting /dev/ttyAMAO as PTT interface
c) run soundmodem as usual : it will direct the PTT signal on the CTS0 pin
of the UART.
d) the CTS0 pin can be actually (RaspberryPI B+) associated to the GPIO pin
17 (BCM mode)when the pin mapping it's set in ALT3 MODE. The "ALT mode"
(alternative pin mapping matrix in the RaspberryPI) switch can be easily
made by different utilities (for example small "to be compiled" functions
like gpio_alt.c, or alternative Python libraries like "pigpio library" or
other, at the moment it's not managed by standard Python RPi.GPIO libraries
). It's then required to create a small script (Python or bash, able to
switch off SAMBA, sets the GPIO17 in ALT3 mode and finally executes
soundmodem : doing this the GPIO17 can easily drive one of the classic PTT
interfaces without need of heavy and expensive RS232-to-USB HW interfaces.
Enjoy
Ugo Poddine
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