[OZAPRS] HF APRS -2

[Matthew Cook]

That interface card is hideously expensive for what it is;

Other options;

   - The wolfson sound card is less than a third that price including
   shipping from E14, however a syba USB sound card is less than $5 from eBay.
   - PTT is just a transistor of an I/O pin, preferably with a h/w
   monostable timer to prevent locking the transmitter on; I still don't trust
   Pi's with 100Wpep of HF present, box or no box.

Personally I'll be trying a Tinkerboard first since it has onboard
microphone and audio, more grunt that a Pi-3, wifi, BT, I/O and serial
ports. In my case I can read the GPS from within the HF transceiver, which
is already shared three times in the back of the car already.

However will still experiment with STM32 option since this would make a
very nicely integrated option in the new year.

73

Matthew
VK5ZM



On 18 December 2017 at 20:57, Mark Jessop <lenniethelemming at gmail.com>
wrote:

> David Giddy has reminded me off-list of the existence of the UDRC-II:
> http://nwdigitalradio.com/product/udrc/
>
> This is pretty much what I was looking for, with the exception of the
> onboard GPS. A little bit pricier than I was hoping for, but time vs money
> and all that...
> Would require a bit of coding to make whatever modem Glen writes key to
> the relevant GPIO pins, but hey - open source, and I'm more than happy to
> write and test code :-)
>
> 73
> Mark VK5QI
>
> On Mon, Dec 18, 2017 at 7:35 PM, Mark Jessop <lenniethelemming at gmail.com>
> wrote:
>
>> Given the cost of boards like the Raspberry Pi Zero, and other similar
>> boards, I don't see it being targeted at ARM-NEON being that big of a deal.
>>
>> I guess a good product to complement the modem would be a 'shield' (or
>> hat, or cape, or whatever the kids call them nowadays), for a raspberry pi
>> or similar, that includes:
>> - An Audio codec chip (probably via I2S? Example DAC board here, but no
>> ADC: https://core-electronics.com.au/pimoroni-phat-dac-for-raspbe
>> rry-pi-zero.html)
>> - PTT interface (relay? FET?)
>> - Maybe even a GPS unit? (Something like a uBlox MAX-8 would go nicely)
>>
>> Of course you can do a lot of this with a USB sound card and some
>> external circuitry, but I like the idea of a self-contained unit that you
>> could mount in a small box.
>>
>> I might look into parts for such a board over the holidays, if I'm not
>> too busy chasing balloons at Mt Gambier...
>>
>> 73
>> Mark VK5QI
>>
>> On Mon, Dec 18, 2017 at 1:22 PM, Glen English VK1XX <
>> glenlist at pacificmedia.com.au> wrote:
>>
>>> Matthew Cook asked me about the hardware and STM32 :
>>>
>>> STM32F7 MIGHT run the decoder, for narrow bandwidth search windows and
>>> slightly higher SNR requirements (+1 dB say) . The search algorithm is
>>> intensive and the LDPC decoder is hard work, also. But there is a nice
>>> vernier control on the "how hard it tries" to control CPU usage.
>>>
>>> STM32-anything will definitely run the encoder (lots of LUTs in FLASH)
>>>
>>> (it already is implemented on STM32L151 back in 2014)
>>>
>>> talk soon when I am not so flat out
>>>
>>> cheers
>>>
>>>
>>>
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>>> OZAPRS mailing list
>>> OZAPRS at aprs.net.au
>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>>
>>
>>
>
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