PWM Frequency
 

Hi,
Well I have another question. The DC motors I asked about in my last thread are originally Sanwa Servo motors. I tried to plug in the servo motor to the pwm port in the controller, but it didn't control the motor properly. How do I know what the frequency of the pwm should be in order to control the motor?
Is there a way to change the controller PWM frequency?

Re: PWM Frequency
 

Well, i know I have been asking loads of questions recetly, but I hope you are still willing to answer me.
I have a new question.
Is there a way to download programs to the controller using RJ-11 to COM cable instead of the VEX orange cable?

I tried to do that but it didnt work.

Is there a way to do that?

Thanks again,
Guy

Re: PWM Frequency
 

Guy,

Yes.

We had an old laptop with a serial port but no USB port and we were successful in programming a VEX controller with it...

If you look at the orange cable, you will see that it comes apart at the DB9 connector. Take it apart at that connector.

One half is a USB to serial converter and the other half is a serial to RJ-11 cable.

The mounting hardware on the DB9 forced us to use a standard (straight through), M-F, DB9, serial extension cable (IFI P/N CABLE-DB9-6FT-MF) between the computer's serial port and the orange cable's DB9.

Make sure that the IFI_Loader software is configured to the proper port. In our case it was COM1.

It worked like a charm...

Mike

Re: PWM Frequency
 

Guy,
I did a search and found a Q&A on an RC forum that the PWM pinout on the Sanwa Servo is different then the HiTec or other manufacturers. You need to check the part data sheet for your Sanwa against the pinout for the other motors.

Re: PWM Frequency
 

When I tried to use my RJ11 to Serial cable, the loader couldn't find the controller. It said "No programming board found". I tried to switch the COM ports, but still it couldn't find anything.

Any suggestions?

Re: PWM Frequency
 

Guy,

Was the Baud rate set correctly?

Did the VEX controller LEDs indicate that the controller was ready to program when you pushed the program button?

You said that you switched the COM ports... Did you verify the active COM port using the Device Manager?

Mike

Re: PWM Frequency
 

All the settings were the same as if I were downloading the program using the orange cable (accept the different COM port).
As far as I know, there is no button to push in the VEX controller.
And my serial port is located on COM 1.

Re: PWM Frequency
 

accept=except (what a stupid mistake)

Re: PWM Frequency
 

Guy,

When you used the orange USB to RJ11 cable to program the VEX controller, you have to press the button on the cable to do it...

When the orange cable is taken apart at its DB9 connector, the program button is between the DB9 and the RJ11 connectors.

Also, insure that COM1 is set to 115K baud in the Device Manager so that it agrees with the IFI loader.

Mike

Re: PWM Frequency
 

Guy,

Your English is quite acceptable (considering your country of origin).

I take no exception to small mistakes. ;-)

Mike

Re: PWM Frequency
 

I think you didn't understand my question. I have a cable, which has nothing to do with the VEX orange cable.

The cable is RJ11 to serial and I want to use it instead of the orange cable.
The reason I want to do it is because I have 2 VEX controllers, and only one cable and I need two (one is not mine). In order to buy a cable I need to buy the entire programming kit which costs about 100$. I want to save my money and use my own cable.

I hope Im clear now...

Re: PWM Frequency
 

Guy,

OK... There are three paths which you may follow...

1. Contact IFI via the VexForum and ask how to purchase the cable you want.

2. Contact IFI via the VexForum and ask for a schematic for the DB9 to RJ11 cable (with programming button) and modify your cable appropriately.

3. Take the orange cable which you already have. Using an ohm-meter, trace out each of the RJ11 pins back to the DB9 and determine which pins go where on the DB9 (at least 2 pins should connect). Then determine which pins get shorted out when the programming button is pressed (most likely the 2 unused by the DB9) and modify your cable appropriately.

Best of luck...

Mike

Re: PWM Frequency
 

Thank you very much for your advices.
You have helped me alot!

Re: PWM Frequency
 

This may seem a bit off topic than what you guys are talking about, but how exactly can you program the vex controller with MPLab?

Re: PWM Frequency
 

Exactly the same as the FRC robots. Put another way, If you can program a FRC robot, you can program a FVC robot.

The FVC controller has exactly the same uC as the 2004 and 2005 FRC controllers. The differences due to the hardware "glue" around the uC are almost invisible to most users. In most cases, if you choose your I/O correctly, you can cut and paste your FRC code into a FVC, compile and run.

Do you have a specific question?