122 posts in this topic

Posted · Report post

I measured all 3 at the SMA connector with their own pigtail installed. Your remark makes sense, even if 3-5dB sound like a lot of difference for a little pigtail to me... I'll try that when I have time.

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Then I've tackled the GPS, I didn't want to buy the FrSky unit as I already have tons of modules in my drawers, but obviously that involved finding out what the sensor hub was happy with. Found out with some help that it wants 9600,N,8,1, default NMEA sentences are fine, 1 or 2 Hz. Data is transmitted at 1Hz, but it seems setting 2Hz helps truly getting 1Hz downlink (input and output both at 1Hz but unsynchronised = gaps sometimes).

I purchased the Frsky hub and GPS. The uBlox GPS they use defaults to 9600 baud / 1 Hz. But during power-up the hub reconfigures the GPS to a much faster update (perhaps about 5Hz, but that is just a guess).

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I decided to go forward with the DiY FrSky GPS-hub using a PIC. I've got a crude working prototype at this point, but the GPS parsing engine needs more work. My biggest issue at the moment is a bit silly -- I can't get a GPS satellite fix while indoors. Working outside in the rain is a bit of a problem. It's the simple things that slow down projects like these.

So I'm on the hunt for a work-around. Despite my distrust of "free" software, I've downloaded two different GPS simulators. The Skylabs GPS demo app was a total bust (would not recognize any com ports on my WIN7 PC). Another one named SatGen was initially helpful, but is buggy and does not provide RMC sentences. So, does anyone know of a good/reliable/trojan-free NEMA simulator that can provide RMC and GGA sentences? I don't want to have to buy it, so hopefully there is something out there that is a freebee.

EDIT/Update: It just dawned on me that my old Garmin Handheld GPS has a NEMA simulator mode. I used it several years ago during a prior GPS project. So I will dig it out of storage and put it to work. With luck, I expect to have more DiY FrSky GPS-Hub progress in the next couple days.

Edited by Mr.RC-Cam
Update

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Posted (edited) · Report post

Well, my solution back during development of the IFOSD was plain and simple... I recorded a few minutes of NMEA into a plain text file, then played that back to the serial port with Hyperterminal, with a line delay to slow it down...

Other than that, great news about the PIC job :)

Edited by Kilrah

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Posted · Report post

Well, my solution back during development of the IFOSD was plain and simple... I recorded a few minutes of NMEA into a plain text file, then played that back to the serial port with Hyperterminal, with a line delay to slow it down...

Good idea. I'll use the Garmin's demo mode as a data source and capture an hour's worth of NEMA sentences. Then I'll use your Hyperterm method and play back the file to the Hub so I can work on the GPS parsing code. The reason for doing it this way is because the Garmin eats batteries at a fast rate and using the data from a file eliminates the dead battery issues while I debug.

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Posted · Report post

With tracker, Spektrum and everything working fine my FPV Sbach UMX is getting closer :)

Closer than expected actually, found a wide lens I could use with the camera...

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Posted · Report post

Fantastic video!

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Posted · Report post

Paul B Mather (Happykillmore) wrote an easy to use GPS emulator as part of his GCS for the Ardupilot series of products. Try DIYDrones.com.

Peter

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Posted · Report post

Thanks for the DIYDrones/Happykillmore emulator tip.

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Posted · Report post

Good news, the DiY FrSky GPS hub prototype is fully working. I need to do some code clean up and then determine which PIC chip to port it to. Unfortunately it wont be a 8-Pin chip, but there's some 14 pin choices I can use. Currently I have it running on a 18 pin part (because it is the smallest PIC chip my compiler can support that has a ICD debugger feature in it).

I mapped the GPS's Fix Status and Satellite count into the FrtSky's Temperature2 and Fuel Level registers. So now GPS signal status/quality can be seen on the R/C transmitter's telemetry display screen. I have also increased the update rate to the GPS data. I can do more tricks like this, but I can't think of anything else that should be included. Any wish list items I should consider?

There's a tremendous amount of flexibility in the way the Hub can be implemented. For example, there is room in the FrSky 8-ch Rx to install the Hub chip inside the case. Power would come from the Rx's 3.3V Vreg to eliminate an external Vreg. Or it could be installed on the GPS and steal power from the GPS module's Vreg. Or make it standalone (but it will need 3.3V power).

I'm not too keen on a sloppy dead-bug wired chip and would prefer using a PCB. But if I go to the expense of doing that, I would probably add the baro sensor too. And perhaps some other features. With luck, it could all still fit in the 8-Ch Rx's case.

Kilrah, I know what you had in mind (basic 8-pin chip, a few hand soldered wires, GPS module, and that's it). We have similar needs, but I want it to have a bit more functionality. Especially since the added features are nearly free, so to speak. Do you have any thoughts about this? Is there any interest in a custom PCB?

If there is any further interest in the project then I will spin it off into a dedicated thread. Otherwise, this will just be another one of my many projects that earns a check mark on my DiY bucket list. :)

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Posted · Report post

Good news :)

Fix status is good! I don't have any other idea right now...

I'd be very open to a small PCB with baro that fits in the RX's case! Heck I could maybe even fit the GPS in there - not sure it wouldn't be jammed by the transmission though.

If possible, maybe also have appropriate wiring for easy connection to the D4RII?

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Posted (edited) · Report post

And on my side:

As I plan to sell all my other R/C TXs and keep only the 9x, I got myself a 20€ 2nd hand Graupner synthesised 35MHz module for occasional reuse of some 35MHz receivers I have - for example if I need to fly with 2.4GHz video gear.

As the new 9x has no more integrated antenna, plus I have reused the module antenna pin for serial FrSky comms, plus I use the antenna hole to attach a video recorder, I needed another way to put a 35MHz antenna.

I simply made a little 2-piece mount that I glued on the module case. Even with the weight of the deployed antenna the module hooks seem to hold well enough. Just hope the glue will hold too :mrgreen:

Of course the PCB trace going to the module case pin has been cut, and there was a nice little pad available to solder a wire to go to the antenna. The antenna was scavenged from an old MHz TX.

DSC00860_ss.jpg

DSC00862_ss.jpg

Edited by Kilrah

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Posted · Report post

I'd be very open to a small PCB with baro that fits in the RX's case!

Sounds like a plan. The baro altimeter function needs a couple pins for I2C and about 2K of code space. So I will keep that in mind during the final PIC selection. It will take a few weeks for me to design a PCB and get them fab'd. Do you have any soldering issues with really small parts such as QFN IC packages or 0603 size resistors?

As I plan to sell all my other R/C TXs and keep only the 9x, ...

Wow, the 9X must really have made a new friend. I have to admit that with FrSky telemetry and ER9X firmware, it works amazingly well and looks good too. :)

My LCD backlight arrived a few days ago. So I get to open up the 9X again and install it. Just another thing on the hack project to-do list.

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Do you have any soldering issues with really small parts such as QFN IC packages or 0603 size resistors?

0603 is a piece of cake, but I don't have any hot air equipment, so the things with no pins might be another story... If the pads stick out enough to accomodate the iron's tip it should be possible...

Wow, the 9X must really have made a new friend. I have to admit that with FrSky telemetry and ER9X firmware, it works amazingly well and looks good too. :)

It really has. I'm going to sell a $2500 TX and buy 2 more $60 TXs :)

I bought my T14MZ 5 years ago because it was the only one that really offered the total programming flexibility that was so useful for FPV, but the main functions that were important for me were free channel number assignments, flexible trainer input (use the transmitter's settings, choose individual channels, reorder channels,...) and multiple D/Rs. To have this I had to put up with a pricy and heavy TX, while the big screen is nice the interface is slow, the 2s/2200mAh pack has 2 hours battery life and a spare costs $100... the list goes on.

Actually with open9x I can do all these much more conveniently (it takes me about 1/4th of the time to program a model on the 9x... no need to go back and forth between slow menus, no need to have to put up with predefined mixes that sometimes aren't exactly what you want or are so complicated with 10x the number of options you need that you spend 10 minutes just finding the one that will do what you want, no need to look at the screen to find the +/- touch screen zones - yeah, sounds stupid, but truly annoying, some menus like the end points are ridiculously annoying to set), AND I can do more, i.e. telemetry, Spektrum, power my goggles straight out of the TX,...

It should really be the only TX everyone uses, I don't find any other offers something extra really - and if one did, it would just be a few hours of programming away to add it :D

For the moment there is one only thing that's missing, having an RF part with more than 8 channels. It should come soonish with FrSky, but in the meantime I just ordered a 2nd hand 12-channel JR-style FASST module for 60€. So I should get 12-channel capability with Futaba receivers (or 2 HK OrangeRX (FrSky really) TFR8S as one can be set to output CH9-14).

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Posted · Report post

Kilrah,

Your idea, using the 35 MHz module, is brilliant!

I realized that I have an old Graupner module - now I can use it together with the Turnigy 9x :) .

How are the connections made?

Can I just plug it in ? (of course connect the antenna externally). Are the voltages OK ? (Battery voltage and PPM level)

Regards Pete

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Posted (edited) · Report post

Yep, just plugged in. I must say I haven't checked RF power and voltage dependency yet, that would be some homework I'll have to do at some point... It's possible my 2s supply could cause problems, the Graupner TXs were usually running on 9.6V.

At least it works fine at close range in the workshop with antenna collapsed at 7.6V battery voltage, so PPM is OK and it does transmit, tested with 3 different receivers (1x ACT4DSL, 1x Corona Synthesised 8CH , and... I don't remember the 3rd one, but all on different channels).

I did fly a quad indoors with it earlier today :)

If you haven't reused the antenna pin on the 9x' module connector like me, you could even mount the antenna in the TX.

Edited by Kilrah

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Posted · Report post

It should really be the only TX everyone uses, I don't find any other offers something extra really - and if one did, it would just be a few hours of programming away to add it

The hacking community really deserves the credit. For sure, the stock 9X would never have appealed to me. But take a economy priced 9X, toss in a FrSky upgrade, add open source software, and a bunch of hours with the soldering iron, and the results are very cool indeed.

I think some Far East R/C mfg's have been watching too. Walkera has introduced their DEVO-10 ($150 USD) and it is like a 9X with optional 2-way telemetry, plus it is 10 channels out of the box. They even bothered to install a backlight on the LCD. Their DEVO-12 has been out for a bit and it is $500. It has a color LCD interface like the very high end systems. Walkera is not a brand that has excited me, but their activity shows that there will probably be more low cost R/C systems with "high end" features. With luck, some of this stuff might actually work well. :)

Spent more time on the GPS Hub. PCB layout is in progress. It will be only 27mm x 20mm. There should be room for a 3.3V VReg too, so it will be easier to use it in a standalone installation.

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I think some Far East R/C mfg's have been watching too. Walkera has introduced their DEVO-10 ($150 USD) and it is like a 9X with optional 2-way telemetry, plus it is 10 channels out of the box. They even bothered to install a backlight on the LCD. Their DEVO-12 has been out for a bit and it is $500. It has a color LCD interface like the very high end systems.

Well, from what I've read of people who have Walkera TXs they aren't any better than a 9X with stock firmware, and if anything would just be other candidates for a custom firmware... :D

Many are also holding up because Walkera have been good at releasing new, incompatible RF parts with every new TX generation, so investment in RXs is pretty much always a net loss.

Spent more time on the GPS Hub. PCB layout is in progress. It will be only 27mm x 20mm. There should be room for a 3.3V VReg too, so it will be easier to use it in a standalone installation.

Nice :)

BTW, the D4RII is now available here:

http://www.alofthobbies.com/radio-gear/frsky-telemetry-system.html

I ordered a couple with a few Futaba-compatible ones (2x TFR8S, which should be the only current and easy way along with the Robbe FASST module I bought second hand to get 12 channels sent out of the 9x, and a TFRSP for our big hexa).

Oh, and I ordered a 2nd 9x from HK last night using the trick to bypass the backorder restriction, and I just got a stock arrival notification which includes mine :)

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Posted · Report post

Kilrah,

That sounds good. I will test now. I use 8 NiNM cells for the Turingy Tx (the same number as the Grauper used) so there should be no problems with lack of voltage.

I will mount the antenna inside the Tx, and not use the module's antenna pin for anything else.

Mr.RC-Cam,

I will connect my FrSky module directly to the TX/RX of the Atmel processor (as you did).

But, just to check, is the brown cable connected to a ground point in the picture in post #1? (it is difficult so see...)

/Pete

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Posted · Report post

BTW, the D4RII is now available here:

http://www.alofthobb...try-system.html

Poop, just placed an order with them a few days ago and they didn't have it then. Most of my FrSky stuff is from Aloft Hobbies; Good prices and they ship fast. :)

ordered a 2nd 9x from HK last night using the trick to bypass the backorder restriction

What's the trick to workaround the backorder?

But, just to check, is the brown cable connected to a ground point in the picture in post #1?

The brown is ground.

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Poop, just placed an order with them a few days ago and they didn't have it then. Most of my FrSky stuff is from Aloft Hobbies; Good prices and they ship fast. :)

Yep they have stock, have good prices, and postage is cheap even to Europe. Perfect :)

What's the trick to workaround the backorder?

Open the product page, disable javascript in the browser settings, add to cart, reenable javascript. That way the "This product cannot be backordered" popup can't run and gets bypassed :)

As most don't know about this the queue is very small, so you're (for now...) pretty sure to get one from the next shipment...

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Posted · Report post

Yep, just plugged in. I must say I haven't checked RF power and voltage dependency yet, that would be some homework I'll have to do at some point... It's possible my 2s supply could cause problems, the Graupner TXs were usually running on 9.6V.

OK I've done a little test, and the Graupner module works fine down to 7V, then RF power will be slightly reduced but with stable behavior down to 6V. So no problem on 2s, my alarm is at 7V anyway.

I was a bit surprised by the low RF power of only ~14dBm. I checked my other Graupner 35MHz TX (an MX16s) and it's the same. My Futaba puts out a good 22dBm.

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I was a bit surprised by the low RF power of only ~14dBm. I checked my other Graupner 35MHz TX (an MX16s) and it's the same.

25mW is surprisingly low for a 35MHz R/C Tx. As a sanity check, a related test would be to compare *radiated* RF (field strength) of your various 35MHz transmitters with their stock antennas fully extended.

The Turnigy back light kit was installed in my FlySky 9X. The light panel only draws 60mA so it is on full time (I copied Kilrah). Hopefully this is the last time I have to open up the transmitter's case.

The FrSky GPS Hub PCB artwork is nearly done. I won't be able to finish it for a few days, but I expect to order the fab boards late next week. Here's a 3D drawing that shows the layout (subject to change):

post-2-0-04722600-1332379989_thumb.jpg

The board on the left is the GPS-Hub (with baro altimeter sensor IC). The one on the right is an optional add-on board for the G-top PA6B GPS module (a low cost choice). On the backside of the GPS board is the SuperCap for GPS battery backup. Keep in mind that these boards are only 27 x 20 mm, so the SMD parts are really tiny.

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Posted (edited) · Report post

Nice board :)

So this seems to fit in the RX, nice! I guess you'll be making a thin board (0.8mm)?

Today's open9x revision added a custom telemetry screen where you can display 6 values of your choice, so it will be the perfect match :)

My 2nd 9X has shipped, after only 3 days :) :)

Futaba module is on its way too.

Edited by Kilrah

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Posted (edited) · Report post

So this seems to fit in the RX, nice! I guess you'll be making a thin board (0.8mm)?

If things go as planned, the Hub will fit inside the 8-ch Rx. The optional GPS board will be remotely mounted via a 4-wire cable so it can be mounted outside the model (direct view of the heavens). They will indeed be an 0.8mm (31 mil) thick boards.

Today's open9x revision added a custom telemetry screen where you can display 6 values of your choice, so it will be the perfect match

The ER9X does not have that ability (yet). Does open9X allow you to choose the GPS coordinate format too?

Edited by Mr.RC-Cam
Added info about GPS cable.

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