FWIW DTMF can be used to send data more quickly than you'd think. There is a requirement for silence after every digit, which makes it seem slow, but you can drop that silence if the next digit you transmit is different from the current one. Using "_" for 50mS pause and "." for no pause, a string of same digits is slow, 1_1_1_1_1 but different digits is fast 1.2.3.4.5 Real data would look something like this: 1_1.3.2.5.4_4.
On Tue, Jul 2, 2013 at 5:58 AM, Pertti Kellomäki <[email protected] > wrote: > Hi Stuart, > > Thanks for the pointers. > > On Tue, Jul 2, 2013 at 1:37 PM, Stuart Longland (VK4MSL) <[email protected] > > wrote: >> >> 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. >> > > Yes, the sending end can indeed be very simple. If there is a transmission > error, the phone application can simply ask the user to try again. One > twist in my application is that I want to produce actual sound, not feed > the signal into a microphone jack, but it won't probably make much > difference. > -- > Pertti > > > _______________________________________________ > AVR-chat mailing list > [email protected] > https://lists.nongnu.org/mailman/listinfo/avr-chat > >
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