AFSK with Picaxe (?)

RogerTango · Apr 3, 2011

I was curious, if anyone was doing any sort of FSK or Bell 103 type modulation and/or demodulation with the Picaxe?

I am wanting to be able to send digital data over audio using the Picaxe as the MODEM.

This would be for ham radio, I want to be able to use it either FM or SSB (2m and HF).

If not, is there anyone interested in co-development of something like this?

The objective is to have a minimalist circuit design. Something in the likes of the 20X2 would be a nice target chip to use.

Thanks for viewing,
Andrew

Nigel Goodwin · Apr 4, 2011

I would have thought the Picaxe is FAR too slow.

KMoffett · Apr 4, 2011

You might also ask this over at the PICAXE forum:PICAXE Forum - Powered by vBulletin
Do a forum search there for: FSK*
71 threads...(the "*" is for padding...vBulletin won't do 3 letter searches.)

Ken

MikeMl · Apr 5, 2011

Look at the schematic of the Byonics TinyTrakIII. It is generating '103 tones directly.

Nigel Goodwin · Apr 5, 2011

MikeMl said:
Look at the schematic of the Byonics TinyTrakIII. It is generating '103 tones directly.

But presumably not using a Picaxe?.

MikeMl · Apr 5, 2011

No, but it does use a PIC

Nigel Goodwin · Apr 5, 2011

MikeMl said:
No, but it does use a PIC

Completely different question though

You can do it with a PIC, but a Picaxe is far too slow as it's a BASIC interpreter - pretty amazing devices though, and cheap with it.

KMoffett · Apr 5, 2011

Slow? The PICAXE 20X2 can run at 64MHz.

Ken

Nigel Goodwin · Apr 5, 2011

KMoffett said:
Slow? The PICAXE 20X2 can run at 64MHz.

Ken

The processor runs at that, the code doesn't.

KMoffett · Apr 5, 2011

Does not a 64MHz processor process the code faster than a 4MHz processor?

Ken

Nigel Goodwin · Apr 6, 2011

KMoffett said:
Does not a 64MHz processor process the code faster than a 4MHz processor?

Ken

Yes, 16 times faster - but it's still just a BASIC interpreter, which only runs at a tiny fraction of the speed of the PIC itself.

RogerTango · Apr 10, 2011

KMoffett said:
Does not a 64MHz processor process the code faster than a 4MHz processor?

Ken

My thoughts also. I ran my 20X2 at various speeds, and it is AMAZING. Im sure even at 16 or more MHZ, *something* could be banged out in code.

Andrew

blueroomelectronics · Apr 10, 2011

Might want to migrate to a regular PIC, you can do very tight timing code in assembly.

Mr RB · Apr 10, 2011

I would think it's quite possible. Something like a Bell 102 FSK only requires a single 1200Hz pulse or two 2200 Hz pulses to represent 0 bit or 1 bit.

And it should be pretty easy to generate either pulse pattern using the PIC PWM module or CCP module and timer interrupt, even if the BASIC interpreter is a bit slow.

RogerTango · Apr 10, 2011

Mr RB said:
I would think it's quite possible. Something like a Bell 102 FSK only requires a single 1200Hz pulse or two 2200 Hz pulses to represent 0 bit or 1 bit.

And it should be pretty easy to generate either pulse pattern using the PIC PWM module or CCP module and timer interrupt, even if the BASIC interpreter is a bit slow.

Would you care to collaborate with me and whoever else is interested in tinkering with a project of such?

Nigel Goodwin · Apr 11, 2011

Mr RB said:
I would think it's quite possible. Something like a Bell 102 FSK only requires a single 1200Hz pulse or two 2200 Hz pulses to represent 0 bit or 1 bit.

And it should be pretty easy to generate either pulse pattern using the PIC PWM module or CCP module and timer interrupt, even if the BASIC interpreter is a bit slow.

Generating it is probably plausible, but receiving it isn't - and he asked for using it as a MODEM, not just a transmitter.

Mr RB · Apr 11, 2011

Sorry Nigel I was under the impression from his first post it was to "send digital data over audio" which I took to mean a very basic "send" FSK.

RogerTango- Sorry I'm not interested in collaborating on the project, I don't use PICAXEs.

You might want to google a bit around the HAM sites for people sending digital data over the radio, as there is probably quite a few projects and products out there already.

blueroomelectronics · Apr 11, 2011

Microchip has a dsPIC Soft Modem Library.
**broken link removed**

The PICAxe is a fun beginners chip but it's like a bike with training wheels.

RogerTango · Apr 12, 2011

I found this post to be very informative, and promising:

Low power 433MHz Telemetry System - PICAXE Forum

Chip is about $10USD:
FX614P3 - CML Microcircuits

I may have to diddle with this one!! Got too many projects I want to
work on at one time! HA HA!

Andrew

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