# Log-o-matic needs logic flip

**URL:** <https://community.sparkfun.com/t/log-o-matic-needs-logic-flip/4044>\
**Category:** Development Boards\
**Created:** [March 31, 2007, 3:05am UTC](https://community.sparkfun.com/t/log-o-matic-needs-logic-flip/4044 "2007-03-31T03:05:12Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![danstrider](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@danstrider](https://community.sparkfun.com/u/danstrider)\
**Post date:** [March 31, 2007, 3:05am UTC](https://community.sparkfun.com/t/log-o-matic-needs-logic-flip/4044/1 "2007-03-31T03:05:12Z")

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This may be a long shot, but I need to flip the logic of the logomatic from non-inverted to inverted to match the uBlox SAM LS GPS. Don’t ask how long it took to figure this one out. I can get the logomatic to work fine with the non-inverted logic on its own, also I’ve been reading the GPS several months now with no problems on its own too, so I know this isn’t a hardware problem by any means. I combed through the logomatic code but couldn’t find how or where the logic is defined. Does anyone know, can I change the logic in the logomatic software? Or, is there a hardware solution? I’m researching changing the logic of the GPS, but that is leading to dead-ends as well.

Any friends have a good answer?

Oh by the way, here’s my project so you know it’s not just a random question that won’t ever go anywhere … this is going on a UAV of sorts that is emulating how birds soar for hours on end: [http://soaring.goosetechnologies.com](http://soaring.goosetechnologies.com)

Thanks for the help.

Dan

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**Author:** ![danstrider](https://avatars.discourse-cdn.com/v4/letter/d/ba8739/32.png) [@danstrider](https://community.sparkfun.com/u/danstrider)\
**Post date:** [June 28, 2007, 7:23pm UTC](https://community.sparkfun.com/t/log-o-matic-needs-logic-flip/4044/2 "2007-06-28T19:23:39Z")

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Is there any interest in making an option to invert the logic? Is there a way to just do this in software so the hardware doesn’t have to change?

Thanks!

Dan

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**Author:** ![Nullz](https://avatars.discourse-cdn.com/v4/letter/n/a3d4f5/32.png) [@Nullz](https://community.sparkfun.com/u/Nullz)\
**Post date:** [June 29, 2007, 4:04am UTC](https://community.sparkfun.com/t/log-o-matic-needs-logic-flip/4044/3 "2007-06-29T04:04:15Z")

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This sounds like you have a voltage level shifting issue between TTL and RS232.

From the SFE datasheet, it looks like the Logomatic is a TTL device from 0v to 3.3v for the RX and TX pins.

Does your uBlox GPS output TTL voltages or RS232 voltages? If your uBlox GPS is RS232, then a MAX3232 will solve your issues. If your uBlox GPS is TTL @ 5v, then a simple voltage divider will do. If your uBlox GPS is TTL @ 3.3v, then please describe your setup more clearly.

How are you reading your uBlox GPS? To a PC directly to a serial port or USB-to-RS232 adapter?

Also, if your uBlox is infact RS232 voltages, you could damage the Logomatic. RS232 voltages can be from -15V to +15V.

Nullz