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Cortex UART questions 
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Joined: Fri Jul 08, 2011 11:38 am
Posts: 4
Post Cortex UART questions
Hi, I'm experimenting around with the serial ports on the Cortex microcontroller with the current version of ROBOTC and firmwares.

Couple noob questions of someone could help me:

1) I am able to program UART1 fine, however UART2 seems to be used by some system purpose. I am hoping to use both UART's on an autonomous program, no need for joystick or wifi Vexnet stuff. Is it possible to use UART2? Is the debugger using it? I am programming the Cortex using the direct USB cable.

2) Why are the constants for 1200 and2400 and 4800 commented out in the BaudRates.h and RobotCIntrinsics.c ?

3) I know this is a hardware question, but are the two RJ-9 on the side of the Cortex labeled RX1 and RX2 different than the UART1 and UART2 connectors on the top of the Cortex?

Thx in advance!

Fri Jul 15, 2011 2:48 am
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Joined: Tue May 15, 2007 9:02 am
Posts: 409
Post Re: Cortex UART questions
Hi dproffer,

UART2 is set up to communicate with the VEX LCD screen by default. If you go to Window > Menu Level > Expert, and then Robot > Motors and Sensors Setup, you will find a tab labeled Serial Ports. From there you can set the UART to be used as "User Program Control".

They were not needed, so they were commented out to safe space.

Yes, they are different. The RJ ports are for connecting to the older, RF communication modules.

Jesse Flot
CMU Robotics Academy
ROBOTC Support

Mon Jul 18, 2011 8:57 am

Joined: Fri Jul 08, 2011 11:38 am
Posts: 4
Post Re: Cortex UART questions
Hi Jesse,
Thanks very much for your answers to my noob Q's!

I've got a much better handle on the serial ports now and have both under my control.

I will uncomment the lower baud rates and see if I can communicate at them, I have one old school slow poke that I would like the Cortex to talk to.

I understand the legacy RF ports now, would be cool to figure out a way to repurpose these for some function, though I am guessing they are controlled by the base controller software.

Thanks again!


Tue Jul 19, 2011 11:51 pm
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