Reading Wireless Air Transmitter using Arduino

[tursiops]

My bad, there's 12 or 13 available, everything following the ID until the 4 battery bits is fair game

I'm also not convinced of the ID encoding, because it is not logical. Decimal 10 has been added to the first three numbers (O, 1, 2), presumably to keep them from having too many zeros in binary. But 4 and 8 are anomalies; 4 has 9 added to it, and 8 has 6 added to it. Makes no sense.

ADDED: it actually DOES make some sense to recode 4 and 8, because otherwise the 4-bit nibble would have 3 zeros in it. The smallest number available for 4 to become is 13 (hence, add 9), and the next fake number if 14, so 8 gets 6 added to it. So the logic is:
IF DIGIT <3, add 10
IF DIGIT =4, add 9
IF DIGIT =8, add 6

 

[TheScubaPanda]

My bad, there's 12 or 13 available, everything following the ID until the 4 battery bits is fair game

Could you give an example tram of transmitting 3500 PSI, I'm a bit confused ...
Maybe even generate an audio file for it

 

[tursiops]

Could you give an example tram of transmitting 3500 PSI, I'm a bit confused ...
Maybe even generate an audio file for it

The pressure is 110110101100

 

[Gone for diving]

Technically very easy with an arduino. Now, making that waterproof with reliable enough hardware ...

Making it waterproof is not that hard for me... its playing with arduino's and talking about this encoding that hurts my head.

When I have nothing to do I would love to spend some time figuring out arduinos

You guys are doing cool things with this thread. Keep it up.

 

[TheScubaPanda]

Is there any trick to play the sound ? If i use my headset or computer speakers it plays some saturated sound perfectly audible. And clearly not working for my dive computer. I tried on Windows & Ubuntu ... No luck

 

[TheScubaPanda]

Making it waterproof is not that hard for me... its playing with arduino's and talking about this encoding that hurts my head.

When I have nothing to do I would love to spend some time figuring out arduinos

You guys are doing cool things with this thread. Keep it up.

If I had access to an old rebreather dive computer with fisher / molex / etc. we could try to design smthg, would be fun

 

[TheScubaPanda]

View attachment 710970
The pressure is 110110101100

So wait, 110 110 101 100 it's 12 digits not 9. I thought it was supposed to be 9 digits long.

 

[rg422]

So wait, 110 110 101 100 it's 12 digits not 9. I thought it was supposed to be 9 digits long.

It can be upto 12 or something, but the proceeding zeros can be left out if the number is less than the maximum.

Is there any trick to play the sound ?

I briefly explained it here: 3. Transmitting the Signal · rg422/PPS-MH8A-Transmitter Wiki
Your not focused on the sound rather the unintentionally radiated RF coming from the coil of the speaker, so as shown in the photo there you have to have the speaker real close to the computer, and even then to get a reliable signal I had to find a sweet spot on my teric. Crank up the sound as high as everything can go and keep playing it while moving your earbud around the computer searching for the point where it will hear it.
Some computer sound cards might just not be capable of clearly transmitting at 38KHz, I know madUKdiver never got his to work.

Look at this PDF, it has some more examples of packets with varying pressures and transmitter ID's:

PPS-MH8A-Transmitter/Examples of Binary Packets.pdf at main · rg422/PPS-MH8A-Transmitter

Decoding the signal used by SCUBA wireless air integration systems - PPS-MH8A-Transmitter/Examples of Binary Packets.pdf at main · rg422/PPS-MH8A-Transmitter

github.com

 

[TheScubaPanda]

Oh so it's not playing ultrasound, it's actually playing RF. Gotcha !

Would a sensor like this for receiving works ? https://www.vishay.com/docs/82458/tssp40.pdf
38 kHz seems to fall under "infrared sensors". Which is kinda weird, I wouldn't have thought it could go through opaque plastics.

 

[rg422]

Oh so it's not playing ultrasound, it's actually playing RF. Gotcha !

Would a sensor like this for receiving works ? https://www.vishay.com/docs/82458/tssp40.pdf
38 kHz seems to fall under "infrared sensors". Which is kinda weird, I wouldn't have thought it could go through opaque plastics.

No that sensor would not work. Remember the 38KHz only means the frequency, cycles per second. That frequency can be transmitted via light (IR) vibration/sound (ultrasonic) or electromagnetic field (radio). Our signal is being transmitted as an electromagnetic field that induces a varying voltage in a receiving coil of wire. Same as AM/FM radio, cell phones, wifi, etc. albeit on a much much lower frequency (VLF band).

What I did was tear apart an old speaker and use the winding of wire as an antenna. For receiving and recording the samples that we used to decipher the signal I used a device built for receiving RF signals. A computer sound card, depending on the max sample rate, can also receive and transmit at 38KHz. Problem is they are quite weak for transmitting, I haven't tried it for recording but it should work fine.

Edit: Frequency isn't really "transmitted" is just a characteristic of the signal. Its the photons, EM waves, or sound waves being TXed.