eZdsp F28335 problem: sudden lost of connection between computer and board.

Hi Ricardo

This is a good indication that your power stage distrubs the USB communication. I can see three ways of overcoming your problem.

1. Limit the MOSFETs turn on and turn off slope by increasing gate resistors. This will of course increase switching losses, but will lower the di/dt and dv/dt. If your product will eventualy go into production you will have to test it for EMI/EMC.

2. Buy XDS510PP+ emulator and hook up the eZdsp to it. The communication between emulator and PC is through parallel port and is less susceptible to EMI

3. Take the usb cable and a ferrite core and make as many turns around it with the cable as you can. This helps, but not as much as the previous two solutions.

Hope this helps.

Regards, Mitja

Mitza has given very good suggestions. On #3, you may try using a shielded USB cable, similar to one avilable from Belkin (p/n F3U13310GLD;

http://catalog.belkin.com/IWCatProductPage.process?Product_Id=17941

Of course, you need to take good care while designing your own board, to pass EMI/EMC test.

Pradeep

i have the same problem, what if i use an optocoupler?

Hi Gaston,

From my experience the interference is not conductive, thus separating the ground with optical isolation, will probably not help.

I know this, because, when developing in a lab, somebody else's hardware (completely isolated) can also interfere with USB-JTAG connection (as it did in my case).

It is also quite expensive (SPI110LV = 1500$) solution, if you consider, that in the end your product will have to go through EMI/EMC testing, thus you will have to suppres whatever is causing interference anyway.

Regards, Mitja

interesting! my problem is that i try to see some signal in one gpio of the ezdsp28335, i use an osiloscope to see it, and then i see the same problem.

I look for the solution on the net, some guys use an optocoupler to work between the dsp and other devices, they use the parallel port on the dsp.

Is very strange that the problem apears when i use the osciloscope. If i want to use the gpio as an enter to the signal that i want to process, then, you say, i have to buy the emulator ($$$$$) or other usb cable.

Then, the people of texas don`t see this problem?

 I mind, how do you work with signals? First you have to do some board to get the sinal and then send it to the dsp. With this you isolate the dsp. So you says, that doesn`t work.

Can you tell me how do you get the signal in your case? or is a secret?

The people who work with this plataform have to use some thing to get signals, or in my case is noise that make this problems apears?

Thanks Mitja to respond.

Gaston.

Hi Gaston!

Just to make it clear. If you load gpio_toggle project form DSP2833x header files and peripheral examples, and you run the example, everything works fine (you can stop/start the DSP, modify registers/variables) until you connect the scope.And there is nothing connected to the ezDsp, or is it?

All of the examples supplied by TI for ezDsp should work regardless if you connect the scope or not.

When exactly does your problem occur? When you coonect GND of the scopt to the GND of the ezDsp, or when you connect the probe with one of the GPIO pins?

Regards, Mitja

Hi Mitja!

What is the difference?

When i connect the probe to the gpio i lost connection. 

Regards, Gastón.

I had this very same problem. The eZdsp board lost connection whenever I turned my power stage on. I have solved this by using a shielded USB cable and placing the DSP board inside a shielded box. I never again lost a connection with the emulator. You can easily make a shielded cable and box with unexpensive aluminium sheets. 

All,

      The Spectrum Digital XDS510PP+ is a very old emulator. Thus driver support is limited. I would recommend using the Blackhawk C2000 emulator, TMDSEMU2000U available from www.ti.com/c2000tools for $299. Then use Pradeep's cable suggestions to work around the noise.

Charlie

Hi all,

Finally I got the XDS510PP+working with the eZdsp 28335 (with a custom connection, otherwise it didn´t work).

And what happens now is that, somehow, this JTAG connector perturbs (or make the eZdsp weaker to the noise, I don´t know) the behaviour of my device (a stepper motor driver with a H-bridge). When the PP JTAG is connected, the current levels in the phases of the motor are not straight anymore, but just unplugging the PP JTAG, they became straight. I guess it makes a loop or whatever that make the board weaker to the emmissions, and thus the ADC reading (any other suggestion to what's going on?).

So, I decided to ask for the shielded USB cable suggested by Pradeep,

http://catalog.belkin.com/IWCatProductPage.process?Product_Id=17941

but I see that the connector is not the same of the dsp board ... any other suggestion of cable?

Thanks a lot,

Ricardo

My thought is that you might need isolation of the target board from the JTAG emulator pod.

Something like the Spectrum Digital Optically Isolated Adapter might be an option.  There may be other options available such as the 14-pin JTAG Isolator on the TI e-Store or the Signum Systems ADA-ISO-TI14.

Hi all again,

Here it goes something curious. 

As I said, when I run the eZdsp with the XDS510PP+, the quality of the control in the prototype goes to something terrible. It is a stepper motor driver, and the waveform of the current became really oscillating. Just unplugging the XDS510PP+, the current become normal again.

Now we are testing a new prototype with the TMS320F28335 integrated with all the electronics of the driver. We use again the XDS510PP+, but this time there is no problem. The control is good whether the emulator is plugged or not.

Is this owe to a bad arrangement in the eZdsp? I don't understand why this happens.

Cheers,

Ricardo.

Hi David,

What can i say, I still have this problem. It cross my mind buy an  external JTAG, because I guess my emulator is dead :(

I don´t know how to solve this problem, I just can say to u what the technical support told me (RE-INSTALL the drivers, after erasing all the register from the computer, RE-INSTALL  the code composer).  I have a nice paperweights of  U$s 500.  here is a link  to see some JTAG http://www.blackhawk-dsp.com/

It cross my mind, that I was the only with this problem. I searched for any answer to this problems in the net, but i can´t find it.  I tried it by changing the usb cable to one shielded ($$$$), it didn´t work, i tried to reboot the JATG also didn´t work. So........

Things that you may try to do:

1) Install the newest version of CCS

2) Contact technical support for propper information

3) Wait to some guru to help you

4)Or buy another JTAG (See the link)

Hope that this problem can have a solution

Regards

Gastón

Hello there,

I have the eZdsp™ F28335 that I works with half bridge dc-dc converter..

The problems happen to me when I increase the input voltage of my dc-dc converter.

The board lost connection to the my laptop

I verified the PWM signals and the amplified PWM signals few times

but after the incident the board cannot produce the PWM signal anymore,only noises.

My laptop and software detect the board just fine,only no output

Do you all think the the internal JTAG of my board is broken?