[OZAPRS] IO PCB audio pTT etc

Glen English VK1XX glenlist at pacificmedia.com.au
Tue Jan 30 21:24:30 AEDT 2018

Hi Matt

Note for PIs, only PI3 will run the decoder decently. any sh1t will run 
the encoder.

How fast can you get the PI off if an interrupt via GPIO comes in ?

In ODROID we have a root process sitting on the IRQ. a shellscript 
shutdown is generated within a time slice or so....

I have a TINY-13 DIL8 atmel on the board to program up to do challenge 
duties for the host. send a pulse, get one back etc within 3 seconds etc 
etc or pull power, and also it has a analog pin for looking at the input 
volts and starting a shutdown on another gpio pin.

just need to have enough energy on board to keep the computer up for 
just long enough to complete a shutdown, in reality probably only needs 
to SYNC and UNMOUNT etc then die. if user files are left hanging the FS 
will deal with that  next boot.
the ups function adds quite a bit to the board, doign it proper.y. I'll 
have a think about it otherwise I'll just provide an opto input to 
accept a closure which will trigger the fast shutdown.

Actually there are a few Raspbian  crash-shutdown type SD card flavors 
(apart from just booting with the system partitions RO and using a USB 
key for /tmp log and application data.)

this is how I do it

send SIGTERM to the guzzling application

ps kill etc

#sync fs
echo s > /proc/sysrq-trigger

#remount in RO
echo u > /proc/sysrq-trigger

echo 1 > /proc/sys/kernel/sysrq or sysctl -w kernel.sysrq=1

echo o > /proc/sysrq-trigger

or really quick and dirty

shutdown -F -h -n now

On 30/01/2018 5:04 PM, Matthew Cook wrote:
> Glen,
> I'd also suggest the following;
>   * pull the TX/RX of the FT230 into a RS232 driver to allow radio control
>   * Have some form of H/W monostable watchdog for the Pi (mostly
>     likely dump power)
>   * It would also be a good idea to have some form of UPS function
>     where it shutsdown the Pi or disables the radio (relay?) when the
>     supply volts are 10.5V or less (programmable ?)
> 73
> Matt
> On 30 January 2018 at 15:36, Glen English VK1XX 
> <glenlist at pacificmedia.com.au <mailto:glenlist at pacificmedia.com.au>> 
> wrote:
>     Today I have done a schematic for a board to plug into either Pi
>     or Odroid, OR any platform with a USB for the usual requirements-
>     audio I/O , PTT, a uart  and some spare pins for GPSPPS etc
>     Before I finalize it, are there any requests ?
>     Currently :
>     40 pin header for direct connection of IO to Odroid or RPi for
>     GPS/UART/PTT/RX mute / IO
>     On board USB audio device (PCM2903) for TX/RX audio  (two channels
>     so can suit  IQ radio)
>     On board USB UART (FT230) for generating RTS for generating PTT,
>     and gives you a 3.3V serial port
>     On board 8-30V in to 5V DCDC converter. quiet.
>     HW watchdog on PTT
>     Some IO for ? (2 x analog in, 2 x uart 1 x I2C)
>     should be buildable for $30 or less. all easy SMT sizes.
>     the idea is you can plug USB audio , USB uart  for any platform,
>     or you can use the built in expansion header IO for PTT etc direct
>     on a suitable board. IE good for PC or good for Odroid/PI.
>     green pluggable header for radio interface.
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