SparkFun Forums

[SparkfunSweden]

I've bought the 9 DOF IMU (SEN-10736) and the FTDI USB Cable (DEV-09717) I downloaded the schema from my Swedish distributor

http://www.sparkfun.com/datasheets/DevT ... 0Cable.pdf

If you look on that Schema there is not question that the cable outputs 5VDC, but the IMU wants 3.3 VCC, I must admit that I have not checked the voltage of the cable yet but im a bit concerned thats why im posting here.

The cable is supposed to output 3.3VDC which is what the IMU accepts. Is the Schema wrong or is the cable wrong? If its the cable what can Sparkfun do to help me get the correct voltage to the IMU?

Thanks...

[Mee_n_Mac]

The cable is supposed to output 3.3VDC which is what the IMU accepts. Is the Schema wrong or is the cable wrong? If its the cable what can Sparkfun do to help me get the correct voltage to the IMU?

Thanks...

This cable outputs 5v. From the product page ...

These have 5V VCC, and 3.3V I/O. The 5V Vcc output shouldn't be a problem unless this cable is being used to power a sensitive circuit such as a sensor.

But if you read the product page for the IMU or look at it's schematic, you'll see it has an onboard voltage regulator and will work with a 5V input for VCC.

The 9DOF operates at 3.3VDC; any power supplied to the white JST connector will be regulated down to this operating voltage
...
•3.5-16VDC input
•ON-OFF control switch and reset switch

It would appear your cable will work if you use the JST connector (or use pins in the header behind it) but this will require that you pull the VCC socket out of the FTDI cable's connector. If you use the pin header (JP7) on the edge of the IMU board, you'll need 3.3V.

[SparkfunSweden]

Thanks for reply

If you look at this clip this guy does not have anything connected to the JST connector (the white one that can take 3.3 - 16V) so he must power it from the USB cable

http://www.youtube.com/watch?v=vVrflj30 ... r_embedded

I cant see anything on the IMU board shematic that would imply that the VCC from the FTDI USB cable will be regulated down to 3.3V on the IMU

[Mee_n_Mac]

I cant see anything on the IMU board shematic that would imply that the VCC from the FTDI USB cable will be regulated down to 3.3V on the IMU

See U5 on page 2 of the schematic.

http://dlnmh9ip6v2uc.cloudfront.net/dat ... or-v22.pdf

This only operates on the VCC coming in from the JST connector though. I can't tell what the cabling used in the video was.

[SparkfunSweden]

He uses the same FTDI cable, you can see that nothing is connected to the jst in the video, so he must power it through the pin on the output header, theres nothing in the schematic about that pin....

[Mee_n_Mac]

He uses the same FTDI cable, you can see that nothing is connected to the jst in the video, so he must power it through the pin on the output header, theres nothing in the schematic about that pin....

So either he's running his 3.3V parts off 5V or (more likely) he's got some (new) version of a cable that uses the 3.3V out of the FT232 IC, like the FTDI basic board does. I can't tell what he's got from the video. For all I know his IMU stopped working 2 minutes after he made the video.

Alternately both the product page and the schematic are wrong (out of date). E-mail SF tech support and see if there's a new version of that cable that's been "fixed".

EDIT : I note that there are non-SF cables which have a 3.3V output for VCC
http://www.ftdichip.com/Products/Cables ... Serial.htm

[SparkfunSweden]

None of those are mine. Heres mine

http://www.lawicel-shop.se/prod/DEV-097 ... ?refcode=f

[Mee_n_Mac]

None of those are mine. Heres mine

Understood. How were you planning to connect it to the IMU board ? If you were going to cut off the connector and solder the wires to the board, you can still do that, just to a different hole for VCC. If you were going to solder header pins to the IMU board, you can remove the VCC socket from the 6 pin connector and do what I suggested above. I guess you could also make an adapter cable to go between the cable and IMU board.

Or return the cable and get a 3.3V one from someplace else.

[SparkfunSweden]

I got an answer from Sparkfun

The I/O on that cable is 3.3V, but the VCC pin is 5V. The microcontroller on the board can handle 5V just fine, but I don't think the sensors can. If you connect this directly to the FTDI port on the board you will most likely fry one or more of the sensors. If you plug the power into the connectors behind the JST connector (or the JST connector itself) you should be fine since this signal is regulated. Let me know if you have any other questions.

Its pretty fun that they market the cable as 3.3V when its only the internal FTDI chip that has that voltage, the VCC is still 5V which render the cable useless direct connected to most FTDI headers.. I could as you say remove the pin from the 6 pin header and route the voltage to the JST. But I really want my Swedish distributor or Sparkfun to supply me with a correct cable. I do not like hacks to get around a faulty product .

[SparkfunSweden]

More problems, when i connect the usb cable to the computer windows does not detect a new devuce and i cant measure any voltage on the vcc pin, the strange thing is that the vcc should be a straight connection from the usb ports 5v pin.. any ways, its probably a faulty cable?

[Mee_n_Mac]

More problems, when i connect the usb cable to the computer windows does not detect a new devuce and i cant measure any voltage on the vcc pin, the strange thing is that the vcc should be a straight connection from the usb ports 5v pin.. any ways, its probably a faulty cable?

If you have an ohmeter you can check the VCC wiring through the cable. It should measure as a few ohms at most. You may not be seeing 5V at the output because the PC's USB controller is not turning it on at the PC end. Some USB controllers are "smart" that way. I"m not sure why the driver is not being requested or installed automatically.

[SparkfunSweden]

It was a production quality problem, the cable socket had lots of remains from the casting which made the socket unable to connect properly. I will get a new one from my distributor.