Exploring the TI Stellaris platform with Energia Arduino-compatible IDE

Introduction

In the same manner as their MSP430 development board, Texas Instruments also have another LaunchPad board with their powerful Stellaris LM4F120H5QR microcontroller. It’s an incredibly powerful and well-featured MCU – which offers an 80 MHz, 32-bit ARM Cortex-M4 CPU with floating point, 256 Kbytes of 100,000 write-erase cycle FLASH and many peripherals such as 1MSPS ADCs, eight UARTs, four SPIs, four I2Cs, USB & up to 27 timers, some configurable up to 64-bits.

That’s a bucket of power, memory and I/O for not much money – you can get the LaunchPad board for around $15. This LaunchPad has the in-circuit debugger, two user buttons, an RGB LED and connectors for I/O and shield-like booster packs:

and the other side:

However the good news as far as we’re concerned is that you can now use it with the Energia Arduino-compatible IDE that we examined previously. Before rushing out to order your own Stellaris board, install Energia and examine the available functions and libraries to make sure you can run what you need. And if so, you’re set for some cheap Arduino power.

Installation

Installation is simple, just get your download from here. If you’re running Windows 7 – get the USB drivers from here. When you plug your LaunchPad into the USB for the first time, wait until after Windows attempts to install the drivers, then install drivers manually after download via Device manager … three times (JTAG, virtual serial port and DFU device). Use the debug USB socket (and set the switch to debug) when installing and uploading code. If you get the following warning from Windows, just click “Install this driver software anyway”:

Once the drivers are installed, plug in your LaunchPad, wait a moment – then run Energia. You can then select your board type and serial port just like the Arduino IDE. Then go ahead and upload the “blink” example…

Awesome – check out all that free memory space. In the same manner as the MSP430, there are some hardware<>sketch differences you need to be aware of. For example, how to refer to the I/O pins in Energia? A map has been provided for front:

… and back:

As you can imagine, the Stellaris MCUs are different to an AVR, so a lot of hardware-specific code doesn’t port over from the world of Arduino. One of the first things to remember is that the Stellaris is a 3.3V device. Code may or may not be interchangeable, so a little research will be needed to match up the I/O pins and rewrite the sketch accordingly. For example, instead of digital pins numbers, you use PX_Y - see the map above. So let’s say you want to run through the RGB LED… consider the following sketch:

int wait = 500;

void setup() 
{ 
 // initialize the digital pin as an output.
 pinMode(PF_1, OUTPUT); // red 
 pinMode(PF_3, OUTPUT); // green
 pinMode(PF_2, OUTPUT); // blue
}

void loop() 
{
 digitalWrite(PF_1, HIGH); 
 delay(wait); 
 digitalWrite(PF_1, LOW); 
 digitalWrite(PF_3, HIGH); 
 delay(wait); 
 digitalWrite(PF_3, LOW); 
 digitalWrite(PF_2, HIGH); 
 delay(wait); 
 digitalWrite(PF_2, LOW); 
}

Which simply blinks the red, green and blue LED elements in series. Using digital inputs is in the same vein, and again the buttons are wired so when pressed they go LOW. An example of this in the following sketch:

void setup() 
{ 
 // initialize the digital pins
 pinMode(PF_1, OUTPUT); // red 
 pinMode(PF_3, OUTPUT); // green
 pinMode(PF_2, OUTPUT); // blue

 pinMode(PF_4, INPUT_PULLUP); // left - note _PULLUP
 pinMode(PF_0, INPUT_PULLUP); // right - note _PULLUP 
}

void blinkfast() 
{
 for (int i=0; i<10; i++)
 {
 digitalWrite(PF_1, HIGH); 
 delay(250); 
 digitalWrite(PF_1, LOW); 
 digitalWrite(PF_3, HIGH); 
 delay(250); 
 digitalWrite(PF_3, LOW); 
 digitalWrite(PF_2, HIGH); 
 delay(250); 
 digitalWrite(PF_2, LOW); 
 }
}

void blinkslow() 
{
 for (int i=0; i<5; i++)
 {
 digitalWrite(PF_1, HIGH); 
 delay(1000); 
 digitalWrite(PF_1, LOW); 
 digitalWrite(PF_3, HIGH); 
 delay(1000); 
 digitalWrite(PF_3, LOW); 
 digitalWrite(PF_2, HIGH); 
 delay(1000); 
 digitalWrite(PF_2, LOW); 
 }
}

void loop()
{
 if (digitalRead(PF_4)==LOW) { blinkslow(); }
 if (digitalRead(PF_0)==LOW) { blinkfast(); }
}

And for the non-believers:

Where to from here? 

Sometimes you can be platform agnostic, and just pick something that does what you want with the minimum of time and budget. Or to put it another way, if you need a fast CPU and plenty of space but couldn’t be bothered don’t have time to work with Keil, Code Composer Studio, IAR etc – the Energia/Stellaris combination could solve your problem. There’s a growing Energia/Stellaris forum, and libraries can be found here. At the time of writing we found an I2C library as well.

However to take full advantage of the board, consider going back to the TI tools and move forward with them. You can go further with the tutorials and CCS etc from Texas Instruments own pages.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.

Improving Arduino to PC Interactions with MegunoLink

Introduction

Through a colleague I was introduced to a new piece of software for the Windows environment which comprises of useful tools that interact with an Arduino-style board (or other MCU with serial data). The software is called MegunoLink, from BlueLeafSoftware in New Zealand. Megunolink has many useful features, and we’ll run through them briefly in this article. They include:

• Serial port monitoring – that doesn’t reset the MCU
• The ability to capture serial port data to a text file
• A tool to graph formatted data sent from the Arduino in real time
• “George” the serial monkey! (see below)
• Enable building Arduino projects using ATMEL AVRstudio
• And Megunolink can also act as a graphical interface for AVRdude to upload compiled code to an Arduino

Installation was simple and straightforward. The installation is only ~1.5 megabytes and not taxing at all. We only have a Windows 7 64-bit machine, so haven’t tested this in emulation under MacOS or Linux. Before moving ahead, note that the software is free. However the developers do ask for a US$10 donation, and if you use the software more than once this is a very fair amount to pay for such a featured piece of software. Now for a look at each of the features.

Serial Data monitoring

As with the Serial Monitor in the Arduino IDE, you can monitor the data from the Arduino, and also send it back through the serial line. Just click the ‘Monitor’ tab and you’re set, for example:

However unlike the Arduino IDE, opening the monitor does not reset the Arduino. But if you do need to perform a reset, a button on the toolbar is provided as shown below:

Capturing Serial Data to a file

Very useful indeed, much quicker than dumping data to a microSD card and then bringing it back to the PC. Just click the ‘Log’ tab, specify a file location and name, then click ‘Enabled’, for example:

You can also append data to an existing text file. When creating the output format in your Arduino sketch, be mindful to have separators such as commas or colons – which make it much easier to delimit the data once imported into a spreadsheet or database application.

Plotting and Graphing Serial Data

Plotting data to a graph is very simple. You simply format the data you’d like to plot using Serial.write commands, and Megunolink takes care of the rest – just click the ‘Plotter’ tab and you’re off.  The data must be formatted as such:

{a, T, b}

Where ‘a’ is the name of the series. T tells MegunoLink to plot the actual real time, and b is the data as a number in string form. Here is a very simple example:

void setup()
{
 Serial.begin(9600);
}

int a=0;
float b,c;

void loop()
{
 for (int a=0; a<100; a++)
 {
 b=a/2;
 c=a*2;
 Serial.print("{a,T,"); 
 Serial.print(a);
 Serial.println("}");
 Serial.print("{b,T,");
 Serial.print(b);
 Serial.println("}"); 
 Serial.print("{c,T,");
 Serial.print(c);
 Serial.println("}"); 
 delay(100);
 }
 for (int a=100; a>0; --a)
 {
 b=a/2;
 c=a*2;
 Serial.print("{a,T,"); 
 Serial.print(a);
 Serial.println("}");
 Serial.print("{b,T,");
 Serial.print(b);
 Serial.println("}"); 
 Serial.print("{c,T,");
 Serial.print(c);
 Serial.println("}"); 
 delay(100);
 }
}

which resulted with:

Here is another example, it is the “SendSineCurve” sketch from the Arduino Graphing library:

You can always save the graph as an image in the usual formats as well as in .emf vector image file format.

“George” the Serial Monkey

This is a serial protocol simulator tool which is useful for testing the control of serial-based devices. You can setup George so that it listens for a particular pattern in the serial output from an Arduino – and then sends back a response of your choice to the Arduino. For example:

For a more detail explanation and detail tutorial on how to control George, see the MegunoLink website.

Arduino Development with AVR Studio 

Using MegunoLink you can develop Arduino projects with Atmel AVRStudio software. As some people find the Arduino IDE somewhat limiting, this option gives you access to the more programmer-friendly Atmel IDE, for example:

Although there is a small amount of tasks to make this possible, it is straightforward to do so, and an easy to follow tutorial has been provided at the MegunoLink website.

Upload compiled .HEX files to Arduino

For those using avrdude to upload compiled .hex files to an Ardiuno, you can also do this using the GUI MegunoLink interface. This is also used for uploading the compiled files generated in AVRStudio, for example:

As with all the other MegunoLink features – there is a relevant tutorial available on the website.

Conclusion

MegunoLink works well, is easy to use, and the price is right. It has to be the simplest tool available for plotting data from a microcontroller, or capturing it to a file without any extra hardware. So download it and give it a try, it won’t cost you anything and I’m sure you will find a use for it in the near future. And remember – if you’re using MegunoLink, please consider making a donation towards the development of further versions. Thanks to Freetronics for the use of their top-notch Arduino-compatible hardware.

In the meanwhile have fun and keep checking into tronixstuff.com. Why not follow things on twitter, Google+, subscribe  for email updates or RSS using the links on the right-hand column? And join our friendly Google Group – dedicated to the projects and related items on this website. Sign up – it’s free, helpful to each other –  and we can all learn something.