Cortex-M4 Kit For Getting Started With Mobile Sensor Apps

Jan. 5, 2012
Technology Editor Bill Wong checks out Texas Instrument's EKS-L4M232 development kit based on a Cortex-M4 Stellaris micro.

Texas Instrument's EKS-LM4F232 board

LM4F232 Cortex-M4 block diagram

EKS-LM4F232 board block diagram

Windows data logger application

ARM's Cortex-M4 is a very popular, low power microconcontroller architecture with DSP and floating point options. Texas Instruments EKS-LM4F232 USB+CAN Evaluation Kit board (Fig. 1) is home to an 80 GHz LM4F232H5QD Stellaris microcontroller (Fig. 2) that includes those options. The 144-LQFP chip also has 256 Kbytes of flash, 32 Kbytes of SRAM, 2 Kbytes EEPROM and Stellarisware in ROM.

I recently had a chance to check out the EKS-LM4F232 Evaluation Kit. While the chip has USB 2.0 and dual CAN controllers, the latter requires addition of a header and matching CAN drivers. I didn't check out the CAN support but board does include USB connections as well as a 3-axis accelerometer and 96 by 64 color OLED screen (Fig. 3). Also, connectors are not installed for the Chipcon wireless evaluation module support.

The evaluation kit comes with cables and the Windows-version of Code Composer Studio 4 on CD. Code Composer Studio 5 is out now (see IDE Based On Stock Eclipse Also Adds Advanced Debug Capabilities) but I used the version on the CD because it matched the sample applications that came with the kit. Both are based on the open source Eclipse IDE. By the way, Code Compose Studio 5 also runs on Linux now.

The board is long with rubber feet so it sits on lab bench nicely. The feet do not block any of the myriad header holes in case you need access to addition interface signals. At one end is a 5-mm screw terminal block for attaching external sensors to the analog inputs. The chip has 3 andalog comparators and dual 12-channel 12-bit ADCs with a 1 Msample/s rate. The board also has precision 3.0-V reference for the ADCs.

Likewise, the sample applications center around data acquisition. There is a microSD card slot for data storage but oddly the kit comes with an empty USB flash drive, not a microSD card. The on-chip flash and EEPROM is sufficient for storing samples for evaluation though.

The board has a pair of USB connections. One is to the chip's USB port that has OTG, host and device support. The other is for the on-board debugger. There is also a JTAG header in case an off-board emulator is used.

Getting started with the Windows-based software is just a matter of popping the CD into the PC. The CD has docs for the Quick Start guide, user manual as well as chip specs and board schematics. The walk through takes less than an hour including software installation ending in a fully tested application running on the board. There is a matching Windows data logger application (Fig. 4) that displays data from the board via the USB connection. The slave application is display only and provides no control over the processor. The logging application provides a new graphical display of sensor input.

The OLED provides a nice on-board interface especially when the board is used in a mobile application since it can run off a small battery (included). There are five user/navigation buttons including select/wake input support. There is also a single user LED that is handy when providing user feedback without turning on the OLED.

The board provides a nice UI with the OLED and button display and easy access to the I/O. I used a logic analyzer and probes to check out the PWMs and dead-band generator support. The chip also has a pair of quadrature encoders making ideal for motor control applications such as robotics.

I also took a little time to check out the latest Stellarisware support. This provides access to a large number of generally useful routines store in ROM as well as runtime that can be stored in flash. It includes things like the Display Driver module and USB support. The Command Line Processing Module provides a basic text command interface that was easy to extend. The Flash Parameter Module makes saving data as easy as calling a function.

There are even math routines that can be handy including the Integer Square Root Module and Sine Calculation Module. The Micro Standard Library provides printf and date routines.

Overall EKS-LM4F232 Evaluation Kit provides a quick way to get hands-on work with the LM4F230 family of chips as well as Stellarisware. It has enough on-board to put together some impressive prototype demos without resorting to soldering headers to the board. Of course, adding the headers provides access to all the features including CAN support.

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