New USB RC interface project - USB interface with PIC16C745

[Isaac]

Hello,

I have just finished a new USB interface project (2:45am here in Brazil).

When Walter Zanette published his project of an USB RC interface, I got inspired to design my own.

My project reads up to 8 channels and appears to Windows as an 8 axis joystick (X, Y, Throttle, Rudder, Dial, Slider, Aileron and Elevator).

I tested it with a Futaba SkySport FP-T6VA (6 channels). Windows 98SE recognized only 5 channels, but Windows XP Home recognized all 6 channels.

The interface works equally well with both signal polarities.

Of course a project that is just like all the others already available is not big deal, so I added some new stuff:

- The PPM signal timing is done in hardware (CCP module of PIC microcontroller). This leads to high resolution/high stability readings. The resolution I obtained was 8192 steps for full stick throw (0.82ms to 2.18ms PPM pulse width), but I divided it by 32, so each channel fits in a byte. If the extra resolution is required, the firmware may be changed. The signal is rock steady, no one can see the slightest jitter in the bars, with the sticks not moving of course

- I added a DC-DC boost converter, to convert the 5V from USB to 9.6V, so the transmitter (the Futaba ones at least) is powered by the interface, via the trainer connector. This way, the RF power section doesn't get powered, just the coding section, so no RF is radiated. The power switch of the TX remains off all the time, the battery is not drained and there is no need to remove the crystal of RF module. This is the best part, I think.

- The project will be published for free, complete with all schematics, source code (under GNU GPL, perhaps), PCB layout, etc.
This way, I hope, several people can enhance my project, to fit other needs.


Some improvements I already envised:

- Multiple USB reports, so the 8 byte report limitation can be broken. This way more channels, with more resolution may be used.

- Channel reordering (nice idea Walter), so the correct functions can be assigned to different TXs brands.

- Add a joystick port to the interface, so it becomes dual-mode: RC to USB converter and also joystick to USB converter. Perhaps two people may use it simultaneously.

The microcontroller is plenty of free pins, so there is room to many ideas...

When I get everything documented and debugged, I will publish it. The only problem is that I don't have a home page to upload it, so I expect someone offers to host the files.

Best regards,

Isaac

[aeropal]

..

[Kim]

Hi Isaac,
Where have you uploaded you USB Interface project?

Regards.
-Kim

[pipercub]

Isaac, i would like to build your interface if i can get drawings and possible the hex file for the ic. I do like the idea of not having to use battery power to the transmitter. If you already have a site or location on where i can download the info would be great.

thanks
pipercub

[Isaac]

I didn't uploaded it yet, because it is not fully documented. When I finish the documentation I will make it available to everyone.

By the moment, I may send it by e-mail as a pre-release version, only the hex file and the electronic project (schematics, pcb, etc.), to who ask it. Please send me a PM with your e-mail.

The current version reports channel 5 as a button, and all other channels (up to 7) as analog axis. This is because in my tx, channel 5 is landing gear, and have only a on/off switch. Of course this may be changed at will, with the source code.

The power output supplies 9.6V (a little more when not loaded). Before plugging your tx, test the voltage with a voltmeter to ensure the voltage is not too high, not to burn your tx.

I suggest everyone to use the PIC16C745/JW (ceramic windowed package), so if things go wrong the part is not lost, and you may upgrade the fimware in the future.

As I don't have a USB Vendor Id, I used 0x0000. I don't know if this may lead to compatibility problems, but if you will sell units of this project, I think it is better you obtain a valid USB Vendor Id and use it in the firmware.

Altough this is a free project, all copyright remains with me, and credits must be kept.

Please note, I will not accept any resposability for any damage that may accur to your RC equipment or computer, arising of the building or use of this project.
Of course I don't expect anything wrong should occur, but I must protect myself.
If you don't know enough electronics, ask somebody more experient to help you.

If you don't accept the above conditions, please don't ask me to send the files to you.

Best Regards,

Isaac

[Kim]

Hi Isaac,
Hmmm. I am still trying to figure out how to send a PM. Appreciate if you could advise.
Thanks.

-ks

[Isaac]

Look at the bottom of my post, there are two buttons, PROFILE and PM. Just click the PM button.

[Isaac]

Just clarifying a question made by PM:

I make the boards in a photolitography shop (they make film masters, "cliche" (I don't know if this the word in english) and Cyrel® stamps for the graphic industries). I send them a PostScript file with the image of the copper, and they send me a etched board the same day, for about US$3.00 ~ US$4.00. The PostScript file is included in the project.
These boards don't have solder mask, so I apply a protective enamel to it.

This is the quickest (and cheapest) way to have a semi-professional quality PCB in hands.

For industry grade PCBs, I use the services of other industries, specialyzed in PCB manufacturing. They require a Gerber set of files (also included in the project). The boards become even cheaper, better quality, with silk screen and solder mask, hot-air leveld Sn-Pb, etc. But they require a larger quantity and the lead time is much longer.

(Long) time ago, I used to draw the PCBs with special pens, then etching by myself with Iron Perchloryde. Very poor results. Other solutions are heat transfer film, transfer stickers, etc.

For programming the PIC, I use PICStart Plus or MPLAB ICD2, both from Microchip itself.
There are several other programming methods, including ICProg, PICProg or PonyProg. These programs require self built hardware to program the PICs, but these hardware are (generaly) very simple to build.

Best regards,

Isaac

[Isaac]

Some people are having trouble with the graphics files.

The gerber files are recognized only by photoplotters for generating the Film Masters.

The PostScript (*.ps) files, are printed directly by PostScript enabled printers (mostly high-end laser printers, the HP LaseJet printers with a "P" in the name for instance).

If you don't have access to such printers, Corel Draw opens the PostScript files.
There are freeware software that opens them too, PSView is one good choice.

Best regards,

Isaac

[Ion]

[Isaac]

[Kim]

Ion,
Which version of G2 did you test the interface on. Does it work on the G2 USB version?

Do you know if it works with Reflex XTR?

-kim

[Cuban Flyer]

Just finished building the interface, works great. I did modify the circuit slightly, but that was for my benefit, I did not use the power section for the TX. I have tested with JR & Futaba with no problems.

Thanks
CubanFlyer

[PRPLARA]

[Serch]

Isaac, only are one version of your firmware?? The 1.00

Thx