USB to TTL help

I have an old GPS unit from an OnStar system and have a couple of diffrent schmatics to hook it up to a computer. My problem is they all call for the RS232 shifter, namely the one from from sparkfun. Any ideas on how to convert that idea to a USB type of shifter as well as being able to use the ground and 5 volt side to power the unit? Any help would be appreciated.

Are you taking about the SparkFun USB Bitwacker? If so are you not wanting to use it because of current limitations.

How much current does the OnStar system draw ?

3v0 said:

Are you taking about the SparkFun USB Bitwacker? If so are you not wanting to use it because of current limitations.

How much current does the OnStar system draw ?

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Not the SparkFun USB Bitwacker but rather like the RS232 Shifter, just with an USB plug, not the RS232 connector. It will need 5vdc. Here is a link to what I am trying to achieve. CLICK HERE

It looks like those programs are using COM1. Unless you can find a USB program or write one that can interface to Google, I would stick with RS232.

No Porgramming Solution

On the PC make the USB look like a COM port. Use a USB>RS232 converter to connect to RS232 shifter which connects to OnStar.

PC side
Microchip has a PC device driver that uses USB but creates a virtual COM port. It will let you use a PC program written for RS232 with a physical USB connection. The UBW instructions help you find and install it.

OnStar side
Get a USB to RS232 converter. If it does not provide the +5 you can open the cable and get it as described in the link you provided.

Power for the module is obtained from a PC USB port. Take a scavenged USB cable and connect the red wire to both the module's +5V pin and the VCC pin of the RS232 Shifter [see diagram above]. The black USB wire is connected to the GND pin of the module and the GND pin of the RS232 Shifter. Now attach the RS232 Shifter to the PC's DB-9 serial port and connect the shifter's RX pin to pin 8 of the module and the shifter's Tx pin to the module's pin 9. Finally, plug the GPS antenna into the module.

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Should work and there in no programming.

Most any USB>RS232 converter should work because only the RX and TX signals are used.

Cool, thanks for the help. What did you guys think of the idea on using the onstar gps module?

woody said:

Cool, thanks for the help. What did you guys think of the idea on using the onstar gps module?

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Depends on what you are going to do with it?