INA700-701EVM: INA700EVM + SCB, PC connection failures

Hello Corey,

Since you were able to successfully flash the firmware, it is likely not a driver issue. Since the error text shows "TI_SCBEVM" that means that the TI-SCB is not recognizing the EVM. make sure the EVM is connected to the TI-SCB when being powered up. It may be worth trying a different I2C address also (maybe GND). Try these steps in this order:

1. Plug your laptop into wall power (in case it is current limiting the USB port)
2. Make sure you only have one tab for the EVM GUI.
3. Connect the EVM to the SCB
4. Power on the SCB
5. Launch the GUI (or refresh the page) and long-press the reset button on the EVM at the same time
6. If something does not connect or times out, try pressing the connect button in the bottom left corner.
   1. If the bulk channel times out, try step 4 again.

If the device is still saying "TI_SCBEVM", then there may be a problem with the I2C pullup resistors. If you have a second EVM that is compatible with the TI-SCB, then you can try connecting that also, to use it's pullup resistors (just make sure the address pins are set high, such as SCL-SCL, so that the EVM finds your other device first.)

Regards,

Mitch

Still cannot connect to the EVM. If I run as a "mortal" user, can't connect to anything even though COM5 shows OK. If I run as an administrator, I connect to the SCB but not the EVM. I did install the drivers as an administrator so Windows is not allowing the GUI to acce3ss the COM port?

I did switch the I2C addresses, no change. I do not have any other EVMs. I guess I can throw a scope on the lines to see if there are any level issues. As shown in the second photo, there is a jumper above the I2C address switch that does not show up in the EVM UG. Tried in both positions, no difference.

I found an issue - note the I2C levels:

Looks like SDA is being pulled up be the EVM. If I disconnect, the SCB can drive SDA all the way down.

Hello Corey,

The jumper you see is only documented on the old version of the User's Guide, the new version has a hardware change that removes the jumper and replaces it with another component. The jumper is to optionally connect the ALERT Bus to the MCU. The GUI does not use the ALERT pin, so it is only for when connecting with a custom controller.

Could you send me another scope shot zoomed in of just one communication frame? Ideally you can use both channels to show SDA and SCL together, but at a minimum I need SDA. Also, try the test disconnecting your connections on the header (IN+, IN-, GND). This way we can help rule out any potential external issues. 

Regards,

Mitch

The external stuff was powered-down in all tests, but fully disconnected for this shot to rule out any strange ground issues:

I also tried a 22 & then 12K between SDA & GND for hahas - no effect, so it seems that INA700 is actually "sourcing" 800 mV - suspicious junction offset? Again, when I separated the EVM from the SCB, the SDA line was pulled all the way down.

Also, any insight as to why things partially work in administrator only?

Thank you Mitch.

cjf

Hello Corey,

Can you also zoom in on the scope shot to show a single I2C transaction (with individual clock pulses)? For example, using a 5µs/div scale.

The I2C pullup resistors are on the EVM, so without the EVM connected, the I2C lines should be floating, which is why it is easy to pull them down. It is almost like your pullup resistor is shorted to power instead of using the resistor....  (or that the resistor is too small). Could you measure the resistance of the pullup resistor with a multimeter? (with the EVM unplugged).

As for the administrator thing, I have not seen that issue before....  maybe your non-administrator account has some restrictions placed on it.

Regards,

Mitch

This EVM is pretty simple - R5 & R6 measure 4.7K as expected. I have nothing else connected except the scope so it definitely seems as though the INA700 is not allowing the line to fully swing.

Waveform w/5 uS/div as requested:

Hey Corey,

I'm thinking you may have a hardware error or short of some sort. As a test, I've updated the GUI firmware to give the MCU a stronger pulldown capability (about 6x stronger), so it would be interesting to see what happens if you download the new firmware. With the new firmware, could you get a scope shot similar to the one above, with a write and a read? (That way we can see the MCU try to pull it down and the device try to pull it down. A read transaction should have some write bits also, so that may be sufficient).

Regards,

Mitch

The stronger pulldown is evident but seems like the issue still persists:

Hey Corey,

Ok, thanks for sending those. In that case I'm thinking there must be a hardware issue or device damage. I'm sending you a friend request through e2e so we can look at the options for you in in a private message. I'll mark this thread as resolved to close it out.

Regards,

Mitch

Still waiting to find out what the next step is. Can a replacement be arranged via E2E? Contact my FAE?