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finn.usa(at)gmail.com
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 Posted: Sat Jul 11, 2020 7:07 pm Post subject: DIY Serial to Gaycode converter |
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Can't find my previous post so here goes.
I was able to use an Arduino Nano to convert serial altitude output from my Dynon D-10A (same from D-100) to gray code altitude inputs on my Garmin GTX 320A transponder.
That replaced my AK-350 altitude encoder. Saved some weight, but mainly I now know that the altitude I see on my Dynon (set to 29.92) is what ATC sees.
I measured altitude inputs on the GTX 320A. Takes less than 0.1mA to pull an input to ground. Internally pulled up to 5V (I measured 4.35V), apparently with a 50K resistor and also has isolation diodes according to the manual.
That means that the digital outputs of the Nano can drive the transponder altitude inputs directly (but needs to be inverted from the altitude table on the aero-electric web site:1 = 0 volts).
http://www.aeroelectric.com/articles/Altitude_Encoding/modecascii.txt
(Note that C4 is LSB and D1 is MSB, so table should be re-arranged as:
[img]cid:part2.BBB064CB.A051C6CF(at)gmail.com[/img]
... to make a lookup table in the program. (I'm sure there is an algorithm to calculate the codes, I just found it easier and safer to use the table.)
The serial altitude output from the Dynon are +-7V volts, so needs to be brought to 0 to 5V for input to the Nano. A 2N7000 FET does that nicely. Source to ground, Drain to Nano input (internal pull-up resistor enabled) and Gate to Dynon output. Gate can handle +-20V, so if handled carefully needs no additional components. Also inverts the signal to what the serial software expects (active low).
Attached program can be compiled and uploaded to a Nano using the Arduino IDE (https://www.arduino.cc/en/main/software).
Remove the .txt extension from the file name (the list server won't allow attachments with .ino file extension).
Accepts -1200 to 125,700', but I assume the Dynon is limited to a lower max altitude.
When you set the Dynon to output altitude in 100' steps, it nicely changes at the displayed 50' points. So if you see 140' displayed you know the transponder transmits100'; 150' displayed transmits 200'.
I programmed it to use D-10A / D-100 format 1 (example):
#AL +05200T+25D7[CR]
(Look for #, then minus sign if there, then digits, then "T". "T" is use as delimiter, rest is ignored till next "#").
1200 baud.
Would be easy to change the program to use any of the other formats and baud rates.
So there you have it: a serial converter/encoder for $6 or less.
Finn
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cluros(at)gmail.com
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| Posted: Sat Jul 11, 2020 7:48 pm Post subject: DIY Serial to Gaycode converter |
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Wonderful, the cheapest available units are $100.
Doesn't the D10A output grey code though?
On Sat, Jul 11, 2020, 20:15 Finn Lassen <finn.usa(at)gmail.com (finn.usa(at)gmail.com)> wrote:
| Quote: |
Can't find my previous post so here goes.
I was able to use an Arduino Nano to convert serial altitude output from my Dynon D-10A (same from D-100) to gray code altitude inputs on my Garmin GTX 320A transponder.
That replaced my AK-350 altitude encoder. Saved some weight, but mainly I now know that the altitude I see on my Dynon (set to 29.92) is what ATC sees.
I measured altitude inputs on the GTX 320A. Takes less than 0.1mA to pull an input to ground. Internally pulled up to 5V (I measured 4.35V), apparently with a 50K resistor and also has isolation diodes according to the manual.
That means that the digital outputs of the Nano can drive the transponder altitude inputs directly (but needs to be inverted from the altitude table on the aero-electric web site:1 = 0 volts).
http://www.aeroelectric.com/articles/Altitude_Encoding/modecascii.txt
(Note that C4 is LSB and D1 is MSB, so table should be re-arranged as:
[img]cid:part2.BBB064CB.A051C6CF(at)gmail.com[/img]
... to make a lookup table in the program. (I'm sure there is an algorithm to calculate the codes, I just found it easier and safer to use the table.)
The serial altitude output from the Dynon are +-7V volts, so needs to be brought to 0 to 5V for input to the Nano. A 2N7000 FET does that nicely. Source to ground, Drain to Nano input (internal pull-up resistor enabled) and Gate to Dynon output. Gate can handle +-20V, so if handled carefully needs no additional components. Also inverts the signal to what the serial software expects (active low).
Attached program can be compiled and uploaded to a Nano using the Arduino IDE (https://www.arduino.cc/en/main/software).
Remove the .txt extension from the file name (the list server won't allow attachments with .ino file extension).
Accepts -1200 to 125,700', but I assume the Dynon is limited to a lower max altitude.
When you set the Dynon to output altitude in 100' steps, it nicely changes at the displayed 50' points. So if you see 140' displayed you know the transponder transmits100'; 150' displayed transmits 200'.
I programmed it to use D-10A / D-100 format 1 (example):
#AL +05200T+25D7[CR]
(Look for #, then minus sign if there, then digits, then "T". "T" is use as delimiter, rest is ignored till next "#").
1200 baud.
Would be easy to change the program to use any of the other formats and baud rates.
So there you have it: a serial converter/encoder for $6 or less.
Finn
[img]cid:part4.21847B4B.F5F8DF0B(at)gmail.com[/img]
Virus-free. www.avast.com [url=#m_7040235781590540538_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2] [/url]
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finn.usa(at)gmail.com
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| Posted: Sun Jul 12, 2020 6:47 am Post subject: DIY Serial to Gaycode converter |
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Nope.
"Dynon's altitude signal output is an RS-232 serial data stream that is
compatible with newer style transponders like the Garmin GTX-330 and
GTX-327. Transponders only accepting the traditional gray code
(sometimes called Gillham code) input require Dynon's optional encoder
converter module." $80
Finn
On 7/11/2020 11:44 PM, Sebastien wrote:
| Quote: | Wonderful, the cheapest available units are $100.
Doesn't the D10A output grey code though?
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cluros(at)gmail.com
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| Posted: Sun Jul 12, 2020 7:04 am Post subject: DIY Serial to Gaycode converter |
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Thanks Finn, I was thinking of the old D10.
On Sun, Jul 12, 2020, 07:51 Finn Lassen <finn.usa(at)gmail.com (finn.usa(at)gmail.com)> wrote:
| Quote: | --> AeroElectric-List message posted by: Finn Lassen <finn.usa(at)gmail.com (finn.usa(at)gmail.com)>
Nope.
"Dynon's altitude signal output is an RS-232 serial data stream that is
compatible with newer style transponders like the Garmin GTX-330 and
GTX-327. Transponders only accepting the traditional gray code
(sometimes called Gillham code) input require Dynon's optional encoder
converter module." $80
Finn
On 7/11/2020 11:44 PM, Sebastien wrote:
> Wonderful, the cheapest available units are $100.
>
> Doesn't the D10A output grey code though?
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finn.usa(at)gmail.com
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| Posted: Sun Jul 12, 2020 7:09 am Post subject: DIY Serial to Gaycode converter |
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Oops. Just noticed a bug in the source code I previously uploaded,
should be:
sAltitude = sAltitude.substring(0, sAltitude.length() - 2);
Otherwise won't see 10,000s of feet.
Attached is the corrected source code and compiled non-test version.
Finn
On 7/11/2020 11:03 PM, Finn Lassen wrote:
| Quote: | Attached program can be compiled and uploaded to a Nano using the
Arduino IDE (https://www.arduino.cc/en/main/software).
|
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AltEncoder.ino.txt |
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