JPI 700 to Android data capture?

Chip Sylverne

Chip Sylverne

Final Approach
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Jun 17, 2006
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Quit with the negative waves, man.
My JPI 700 engine monitor doesn't have a data capture option, but I can download data in real-time through an rs232 serial port and create a log file using a laptop and Hyperterminal. Logging to my N7 would be a whole lot more convenient.

Was wondering if any of you geniuses has data logged serial data to an Android device using a 9pin to USB adapter to an otg cable, and what serial communication app you might have used to capture and create the file?

Thanks.
 
Well, decided to blow this off in favor of a Sparkfun serial data logger. For $25 plus a little $4 project enclosure, I can solve the problem directly to an SD card.

Should work fine and beats the heck out of JPI's $300 upgrade.
 
Keeping an eye on this. I sent it to my partners. Looks promising!
 
Chip Sylverne said:
Well, decided to blow this off in favor of a Sparkfun serial data logger. For $25 plus a little $4 project enclosure, I can solve the problem directly to an SD card.

Should work fine and beats the heck out of JPI's $300 upgrade.
Click to expand...

As a fun project, I built my own JPI EDM-700 Android bluetooth-to-web data capture setup a couple of years ago, and it works great. What I did was to create a little dongle (powered by a long lasting coin battery) that converts the serial output from the EDM-700 to bluetooth (auto-senses the output, so no switch or power cord needed).
I also created an Android app that captures EDM-700 bluetooth feed, sending the data to DropBox, and from there it's picked up by a program that translates it to CSV (spreadsheet format) and plots all the engine parameters as color curves on a JPEG image.
This is then integrated into another application which also receives the GPS track from the flight (from an app on the Nexus 7) and uploads all this data for presentation on a web page that shows all my flights. So this way I have automatic logging of my flights, showing the CHT/EGT/cooling/voltage curves, flight times, max CHT and CYL number (exceedance in red if applicable), max CHT cooling rate (and exceedance in red if applicable), etc. The GPS tracks are clickable into Google Earth display which shows the flight in 3D, including ground speed and altitude plot.

The program auto-detects the origin and destination airports, based on the GPS coordinates (but can be manually overridden).
The only thing that's not yet integrated are my flight videos, which are kept separately at the moment in a manual process.

To retrieve the EDM-700 bluetooth I now use my Android phone (easier than the N7 tablet, which also runs the same capture app).

What's cool about it (besides being much easier than what I had before), is that by the time I leave the plane after a flight, the web page is ready for presentation, so I can immediately view it on my cell phone and see if all my parameters were within the permitted limits or any cylinder was acting up during the flight.
 
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You are a lot better at thinking this stuff through than I am. My solution should be adequate, yours sounds great! Thought about using Bluetooth, but the battery powered adapters seemed pretty spendy. I thought just pulling the chip occasionally to look at the data would be sufficient. You're right about the power cable though.I have a DC outlet in the panel near the serial out , but I'd rather not have the cable at all.

Nice job. Bet you could sell that solution.
 
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The data logger I bought only needs min 3.3v. Don't know the draw. I need to look into running it with a battery...maybe an iPod lith ion or something along those lines.

Must be possible, guys have used it to log data in rc planes.
 
Chip Sylverne said:
You are a lot better at thinking this stuff through than I am. My solution should be adequate, yours sounds great! Thought about using Bluetooth, but the battery powered adapters seemed pretty spendy. I thought just pulling the chip occasionally to look at the data would be sufficient. You're right about the power cable though.I have a DC outlet in the panel near the serial out , but I'd rather not have the cable at all.

Nice job. Bet you could sell that solution.
Click to expand...

Thanks.
I hate wires and batteries, so I chose that solution hoping to only replace the (CR-2032 dual) coin batteries once every few years.
Regarding selling it, I doubt there is enough of a market to justify the effort. I did create a printed circuit for the EDM-to-BT dongle using an online service as an exercise, so at least it looks neat when opened. :)
 
That power solution would give me about 75 hrs at max draw. Not bad.
Form factor would be right.

Still have to remember to turn it on/off though.
 
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Chip Sylverne said:
That power solution would give me about 75 hrs at max draw. Not bad.
Form factor would be right.

Still have to remember to turn it on/off though.
Click to expand...

If you are referring to my coin battery solution, your calculation is about right. And the switch issue really bothered me, which is why I designed it to sense the input signal as an activation or "wakeup" trigger, which turns it ON. After a second or two with no input signal, it goes back to "sleep", or OFF. The input detection circuit is ultra low power MOSFET which draws minuscule amount of standby current, similar to the normal battery shelf life loss.
 
ChrisK said:
Oh man. Any way you could shake lose the code / design on that? This sounds like a huge win, and I'd love to try to port it to iOS for my android-challenged friends...
Click to expand...

There are several independent parts to that project. One is the hardware EDM-700 to Bluetooth dongle, which has only a printed circuit board, some low cost components (probably < $20) and an enclosure.
The receiving app on the Android is fairly simple, but I don't know the iOS side enough to know how hard it would be to port.
The rest is software running on my home server, which downloads the data from DropBox, processes it (matching up the flight data from the EDM with the GPS ground track using their respective timestamps, converting the EDM data to CSV and color curves in a JPG image, etc.), then uploading it to a Cloud based webserver for web presentation (so that it would be available from anywhere).
Not sure how easy it would be to convert to the Apple environment, in my case all the servers run Linux.
The core component is this (or similar) low cost serial to bluetooth module which you can buy from China for a few dollars:

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RotorDude said:
If you are referring to my coin battery solution, your calculation is about right. And the switch issue really bothered me, which is why I designed it to sense the input signal as an activation or "wakeup" trigger, which turns it ON. After a second or two with no input signal, it goes back to "sleep", or OFF. The input detection circuit is ultra low power MOSFET which draws minuscule amount of standby current, similar to the normal battery shelf life loss.
Click to expand...

I think I may steal this idea too. Is MOSFET you used a logic level gate? Did you use an input resistor to protect the source pin? Do you recall the RS 232 signal voltage for the JPI? 3.3v sound familiar?

Got part numbers handy? :D
 
Chip Sylverne said:
I think I may steal this idea too. Is MOSFET you used a logic level gate? Did you use an input resistor to protect the source pin? Do you recall the RS 232 signal voltage for the JPI? 3.3v sound familiar?

Got part numbers handy? :D
Click to expand...

The JPI EDM-700 puts out a typical RS-232 signal, which IIRC is around +/- 7v, i.e. -7v for "space" and +7v for "mark".
At first I was thinking to actually power the circuit using the signal's output, but it became too complicated, so I opted for the above mentioned concept of coin batteries activated and deactivated by presence of the signal.
Before transmission, IIRC, the signal sits at -7v, its idle state.
Since RS-232 may swing between +/- 15v, and I had no way of knowing for sure that +/- 7v was the largest amplitude, I had to allow for that, and be able to detect the negative voltage.
So I decided to use this optically activated solid state relay, that has a built-in gallium arsenide IR LED which drives MOSFET outputs. The Chinese RS-232 to Bluetooth converter I linked above requires a bit of extra current in its "searching" mode, so I had to allow for that. Also, it expects positive TTL-like 0-5v as input signal levels, so the large bipolar signal levels had to be reduced and shifted (for which I used a simple NPN bipolar transistor).
The next challenge was to keep the OFF current leakage to a bare minimum, to maximize the battery life. The above switch is excellent, with leakage in the few pA range. For the "drive" gates that feed the Bluetooth converter I used two enhancement-mode MOSFETs (the low-side n-channel maintains the ON state and drives the high-side p-channel). Their combined OFF state leakage current is low enough to be negligible, so that the main battery life determinant is actual use, as if you had a real switch and used it properly.
BTW, to debug the circuit (and later maintenance), I built a little emulator device using an old laptop with a serial port output, which puts out real RS-232 bipolar signals given an actual EDM-700 data file. This proved very useful and saved many trips to the airport and possible damage to the aircraft.
Hopefully this gives you enough to go on, feel free to ask for anything more.
 
Yeah, it's the bipolar voltage of the rs232 signal that had me scratching my head in using it as a mosfet gate driver. The JPI tech support page indicates it's limited to +- 7v, with -7 idle, as you say. I think what I'll do is leave building the switching circuit until I make sure the data logger does it's job.

I can live with a short power cord for a little while.
Thanks for the help. To be revisited.
 
Chip Sylverne said:
Yeah, it's the bipolar voltage of the rs232 signal that had me scratching my head in using it as a mosfet gate driver. The JPI tech support page indicates it's limited to +- 7v, with -7 idle, as you say. I think what I'll do is leave building the switching circuit until I make sure the data logger does it's job.

I can live with a short power cord for a little while.
Thanks for the help. To be revisited.
Click to expand...

My pleasure. I actually used my own home-made direct cable connection before, hooking up the JPI to my old iPAQ PDA (which also had CV AnywhereMap for navigation), but when I switched to Android I figured it's time to go wireless, as I eventually did. The good thing was that by that time I knew how to process the EDM data, so the digital part was easy.
 
Just for anyone's future reference, I have it on good authority that the SlickUSB android app from Google play and a Trend Net TU-S9 USB to serial converter through an OTG cable to an android device is a good "quick and dirty" way to capture JPI data from the EDM port in your panel without resorting to a laptop.

Haven't tried it yet.
 
Any working serial to BT solution for EDM930?
 
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