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Microcontroller Programming » Off-the-shelf USB to Serial Cable Use

February 23, 2013
by Rocket_Man_Jeff
Rocket_Man_Jeff's Avatar

Hi all, So I'm working on a project that prints data from the MCU to the serial port using the printf command. Using the included cable the data displays properly in Hyperterminal. I happen to have a generic USB to Serial cable that I'd like to use with the finished product to simplify the connection, but things tend to stop working. Specifically, the display in Hyperterminal seems to indicate a baud rate mismatch. I've tried adjusting the baud rate in both hyperterminal as well as in the Device Manager but haven't found a working combination. I am nearly certain that the hardware connections are correct. Has anyone had success using one of these devices?

Thanks! -Jeff

February 24, 2013
by r010159
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The sertal communication on the PC and the cable provided by nerdkits are incmpatible. The nerdkit cable strictly uses TTL (5V and 0V) voltage levels. Serial PC communication (RS-232) uses different voltages (3V, 15V or -3V, -15V) along with other differences like how the voltage levels are used. You would need to build an additional adapter to match the voltage levels. This is in a way documented in the nerdkits manual. So if you get anything at all, it would be garbage.

Hope this helps.

Bob Graham

February 24, 2013
by Rocket_Man_Jeff
Rocket_Man_Jeff's Avatar

Hi Bob, Thanks for your reply. I figured it would be something along those lines. Basically, like you said, all I get is garbage. I recall reading what the Nerdkit cable was, but wasn't sure if this other cable I had laying around was the same thing. Obviously it isn't, but I'm happy to learn the difference. Thanks again! -Jeff

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