21 July, 2013

02 UART communication

Hello, here's second tutorial, also some basic stuff. I'm going to explain how to accomplish communication between computer and lm3s6965. For this task I decided to use serial communication through USB port (COM3-this is something  you can easily find out by using program Terminal Bray, I will explain that later).

For this project you'll need:
- lm3s6965 (Stellaris board, or some other, the principle is the same)
- computer with USB port
- program Terminal Bray
- 3 female connector wires
- USB-TTL / STC-ISP (about few few dollars on ebay, pictures bellow)

Something about our task. We would like to send one character from our computer to the Stellaris and than display that character on OLED.  Here is block scheme, for better understanding and code writing.
I had a little problem in beginning because I had no idea how to write a code for something like this (this was my first project ever whit communication between computer and a chip). And  TI example code wasn't a big help. When I remember all that "problems" it makes me laugh, because it's so simple that I'm almost ashamed of talking "I know how to make successful serial communication between computer and stellaris". 

Now let's get down to business. On my GoogleDrive you can download whole project ith comments. 

If you haven't configure your onboard debugger already, here is little tip how to do that (so that you can download program to the stellaris).

Configuration of OnBoard Stellaris Debugger in Keil uVision 4:

Open this window by clicking on Flash-> Configure Flash tools-> settings should look like there on picture.
After that's completed, Left click on project-> Options for target 'UARTDisplay'... or F7-> Choose Debug and set properties like on picture down here

Now you have to connect Stellaris and USB-TTL to the laptop. Here is picture how to do that. You have to be careful how you connect 3 of that wires. Black one is 3.3V, red one is Tx (because computer transmits data to stellaris) and white one is GND. You probably ask yourselves "why I have to connect 3.3V and GND?". Well it's because when you're not in debug mode, and your stellaris is not directly connected to the computer it has to have some sort of battery.

After that you can Build (Project-> Build target) your project and start downloading (Flash-> Download) it to your Stellaris. When it's done, open Terminal Bray (remember that program from the beginning of this post?! On picture bellow is what you have to set:

COM3 is set by Terminal Bray. It depends on where did you put USB-TTL. Speed depends on your code, where you define it, and when it's ready click connect (on mine picture is disconnect). After all this you can type a letter or a number and it will be shown on you display.

=) Hope it helps!

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