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Topic: Decoding FSk with SoftModem Arduino (Read 19633 times) previous topic - next topic


It works pretty nice even after changing the tone in Arduino applikation. But it wont read transmission from the Android applikation afterwards, I can't change tones definition in Android app. The code from KI4MCW works nice but auto bias is too slow. So I made extra hardware xr2211 because TCM3105 has timing in speed and XR2211 hasn't. Feeding audio to both circuits gives me a delay off decoding 2.5 mS showed by logic sniffer. Hysteresis falling 2040Hz rising at 1360Hz pretty good after considering VCC 5V. At this point I have only bit banging and bit stuffing left.


Thanks for your answer, i'll test it !


This shouldn't give you hard time, only changes I made is in SoftModem.h
#define SOFT_MODEM_BAUD_RATE   (1200)

#define SOFT_MODEM_LOW_FREQ    (1200)

#define SOFT_MODEM_HIGH_FREQ   (2200)


But rx-buffer is quite small, I decided to dump it so far. Replaced it with xr2211 circuit, maybe going back to SoftModem.

Take a look at KI4MCW's arduino_tnc project, using analog input with 3.3V ref, Works better but not perfect for my project.


XR2211 circuit is clearly another option, but it requires external power supply since it needs much more than the 5v coming from USB to work properly.
My goal is to provide HAM radio operators, with who i am working on a sounding balloon tracking project, an easy-to-use and cheap device allowing them to get data coming from radio as a serial input for their laptop or desktop. I already have a software-only solution that uses PC's sound card but it is not very portable and reliable (for hours).

That is the reason why i am interested in using arduino that already comes with USB-Serial interface.
So, i'll give a chance to both solution (arduino soft or hard) !

Thanks a lot again for your help.



Don't tell my circuit that, it's running at 5V nicely. If you want it to be perfect, make a step up converter. The current is only 7mA at 12V supply. I decode APRS nicely at 5V so far, if the audio signal is week it don't decode.


I am not very confident with electronics, i'm rather more familiar with embedded systems programming.
If XR2211 can run properly at 5v it is better for my purpose, as it could be easier to design the hardware part as a shield that could benefit from usb power supply.
I will take a serious look at that with colleagues of mine that are much more efficient with regards to electronics than me (hopefully, i know my limits ;-) )
However, if you have some experience to share about that kind of hardware extension, i will appreciate your help.
But since the discussion goes a little bit off-topic, maybe we can follow it privately.



Sure my email is public go ahead.

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