Re: [avr-chat] Audio modem with AVR

[Stuart Longland]

On 02/07/13 18:27, Pertti Kellomäki wrote:
> Hi all,
> 
> I am planning to implement a simple data logger that periodically
> uploads a small amount of data (< 100 bytes) to a smart phone. I want to
> keep cost at minimum, so I am considering using audio to transmit the
> data inspired by <http://www.ics.uci.edu/~lopes/dv/dv.html>.

You might want to have a look at the AVR implementation of a APRS
tracker device.  APRS is the Automatic Position Reporting System, and
uses AX.25 signalling (1200 baud AFSK) to transmit position and
telemetry information.

The typical set up is a GPS receiver or module communicating on a serial
link, the AVR would implement a NMEA parser and use PWM to generate the
AFSK which would be piped into the input on a VHF or UHF FM transceiver.

Such devices have been implemented with PICs, and I'm sure someone's
done something with AVR.

In your application, you'd basically be looking at the AFSK modulator,
and feeding in your own bit stream from there.  Implementing a full
packet modem with AX.25 would be massive overkill, but the lower level
mechanics are there for what you're after.

Regards,
-- 
Stuart Longland (aka Redhatter, VK4MSL)

I haven't lost my mind...
  ...it's backed up on a tape somewhere.