GPIO

Is the connection you are losing the JTAG connection of CCS to the target hardware?

What kind of probe are you using with the oscilloscope?  Is it a 10X probe or similar?

HI,

I use RTW toolbox of Matlab to send a signal to gpio 0, i have a ezdsp 28335, when i try to measure with oscilloscope (I put the probe in gpio 0 and the gnd of oscilloscope in the gnd of dsp) suddenly a los connection with dsp (warning apears).

I have a Fluke oscilloscope, and the probes are in 1:1. 

First i though that using optocoupler i can measure but someone tell me that dosen`t work. I read a lot of pdf looking for some information of gpio measure, but notthing i can use.

So i have some question to make you:

1) Could be that the usb connection with dsp is sensitive to noise?

2) I work wiht dsp/bios, is an example to see using gpio?

3) If the noise is the cause of the lost of connection, is there a way to eliminate?

4) Someone says that maybe i have to use an emulator, can you tell me if that is correct? 

Is the first time i try to connect something to the dsp, so excuses for the question.

Thanks Brandon.

Gaston.

Gaston said:

when i try to measure with oscilloscope (I put the probe in gpio 0 and the gnd of oscilloscope in the gnd of dsp) suddenly a los connection with dsp (warning apears).

Is this a message or warning from CCS, or another tool that you are using?  I'm assuming another tool, based on other posts that you have made.

Gaston said:

I have a Fluke oscilloscope, and the probes are in 1:1.

I would suggest 10X probes as to not load the signals you are trying to measure.
Do you get similar behavior when simply applying a Digital Multimeter (DMM) to the GPIO?  I realize you will not see the toggling, but it would be good to get a feel for how the measurement device is inducing a change in the environment.

Gaston said:

1) Could be that the usb connection with dsp is sensitive to noise?

It is certainly possible, but I would check other items first.  One way to take the emulation out of the picture, is to put a very simply program into flash, which toggles the GPIO you are trying to measure, such that the device implements this from reset.
In this fashion you can disconnect from USB, eliminating that potential issue.

Gaston said:

2) I work wiht dsp/bios, is an example to see using gpio?

In the DSP/BIOS installation, there are examples provided for the eZdsp2812.  It should be straightforward to migrate these to the eZdsp28335.  I don't believe they showcase using GPIO however, but more about highlighting DSP/BIOS features.

Gaston said:

3) If the noise is the cause of the lost of connection, is there a way to eliminate?

Gaston said:

4) Someone says that maybe i have to use an emulator, can you tell me if that is correct? 

The TMS320F28335 eZdsp Starter Kit has on-board emulation capability through the USB connection.  You can use an external emulation pod, but it is not required.

hi,

The warning message is from CCS, i have another questions:

1) Do you think a optocoupler will work, so the noise don`t make lost connection with dsp?

2) If i want to send to dsp a lot of data, i try to connect the ez430-rf2500, what communication do you say i have to use?

I use the dsp/bios because is to easy to use, when i try to use in the other way, making cmd, i don`t know how to do it, a lot of warning meesage. So if you have a tutorial to send i will appreciate.

This is the first time i`m using dsp.

Sorry for the lot of question Brandon, thanks for respond.

Gaston

hi,

It work fine with the probes in 10:1, however when i desconnect the oscilloscope apears the same warning.

Right now i have the dsp connect to dsp and there is no problem. Is there a secuence to disconnect the dsp?

Thanks Brandon.

Gaston.

Gaston said:

1) Do you think a optocoupler will work, so the noise don`t make lost connection with dsp?

You could use optocouplers, but this will limit the JTAG connection to a few hundred Kbps, rather than frequencies nearing 10MHz for the JTAG interface which more typical.

Gaston said:

2) If i want to send to dsp a lot of data, i try to connect the ez430-rf2500, what communication do you say i have to use?

Is this for your end application?  I'm not sure how this fits in to your objective.  Please explain.

Gaston said:

I use the dsp/bios because is to easy to use, when i try to use in the other way, making cmd, i don`t know how to do it, a lot of warning meesage. So if you have a tutorial to send i will appreciate.

I'm not sure I know what you are referring to.  If you have DSP/BIOS running on the ezdsp28335 already, then the only thing to do at this point is add some code that will be called by a PRD object to do something like toggle a GPIO.  You will likely need to add some code in your initialization routine(s), or main, to setup the GPIO as an output.

Gaston said:

It work fine with the probes in 10:1, however when i desconnect the oscilloscope apears the same warning.

There seems to be a grounding issue, or mismatch in how things are setup.

Gaston said:

Right now i have the dsp connect to dsp and there is no problem. Is there a secuence to disconnect the dsp?

Are you asking how to disconnect the target from CCS?  This can be done with ALT+C in CCS, or the Debug menu.

Hi,

If the optocoupler limit the JTAG connection, what is the other way to make for example a motor control?

If i need to make a control using frecuencies nearing 10 Mhz what do i need to use as interface between the dsp and that i want to control?

Thanks Brandon

Gaston. 

Gaston:

Would you be able to describe your setup that you are testing?

I know that the F28335 eZdsp kit has been used, when connected to a PC directory via the USB interface to develop on.  This is the basis of the platform for our TTO Workshops.  Hooking up an oscilloscope should not have the effect you are observing.

Gaston,

we have permanently scopes connected to our test boards, including the eZdsps, with no problems at all. There is definitely something wrong with your laboratory setup regarding the power supply system. Do you have a ground shift between the DSP and the scope? Are you on different power grid phases with the DSP and the scope? Is your application a  sort of a high voltage application with an isolated and shifted common ground line?

Regards

hi,

i had the oscilloscope probes in relation 1:1. thanks.

I have some question for you. See dsp/bios and headers.