[OZAPRS] IO PCB audio pTT etc

[Matthew Cook]

Glen,

Sounds like a plan.

In terms of UPS what I meant was something monitoring the input volts and
when it gets too low either toggles an I/O or sends cmd (somehow) to Linux
to force it to shutdown nicely.  Then when supply volts comes up > 12.5V it
then boots it up again.  The Pi's don't like having their 5V
unceremoniously dumped in the middle of a write.  The SD card interface
goes pear shaped, bad things happen, big men come.  Nasty business !  Don't
get me started on their USB subsystem and serial ports.

I'm thinking more for the vehicle where you leave it running in the car and
to stop the sucker stopping you from starting it again.  The OpenTracker2
modems Argent Data used to have a MOSFET switched output you could power
the radio through, that was neat for un-attended solar powered APRS
applications.  Sadly when he switched to the DSP decoders in the OT3 series
it wasn't half as good as the original OT2's in terms of weak signal
decoding.

73

Matt
VK5ZM

On 30 January 2018 at 16:49, Glen English VK1XX <
glenlist at pacificmedia.com.au> wrote:

> Hi Matt
>
> excellent  ideas ! will do. OK on the computer watchdog. yep can do that
> to cycle power.  so if the linux stops you dont have to go to site ot sort
> it out.
>
> OK on FT230. and rs232 driver
>
> on the droid (maybe pi) (same pins header I think) there is a bunch of
> peripherals and another uart which I thought could TX to a uart display (or
> I2C), and RXD 3.3V from a 3.3V GPS chip. the interrupt input is on the pcb
> for 1ppm if desired...
>
> UPS of sorts. hmmm maybe a super capacitor. just needs ot go to an IRQ
> capable pin on gpio and halt
>
> How longup time- 100mS ?
>
> yeah BOM will be around $12
>
>
> 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
>> VK5ZM
>>
>> 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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