Now and again we examine various development boards designed for use with the mbed development platform for ARM microcontrollers, such as the the original mbed unit and the Freescale Freedom FRDM-KL25Z – and now we have another one from NXP … their new LPC800-MAX development board:
Although the LPC800-MAX works with the mbed online compiler, you’re not limited to that. NXP have also supplied free offline development tools based on the Eclipse IDE.
The board is based on the NXP LPC812 with an ARM Cortex-M0+ Core running at 30 MHz. The LPC812 has 16KB flash memory, and 4KB RAM. For I/O you have 3 x USARTs, 2 x SPI ports, one comparator, and one I2C port. The serial lines are brought out to a separate serial expansion connector to allow easy connection to a range of expansion boards from the manufacturer. An RGB LED is fitted to the board for all the “hello, world” fun you could want, and for extra I/O (and I2C practice) there’s a four-channel NXP PCF8591 ADC (and also gives you one DAC as well – convenient) along with a PCA9672 I/O expander IC for more GPIO.
If you’re using the offline development IDE you can also make use of the NXP hardware debugging interface as well. Users of the physically-narrow range of NXP LPC development boards will also recognise the two parallel rows of pinouts down the length of the PCB, and Arduino users will recognise the header sockets (more on those later). When you receive the board – you just receive the board, so you’ll need a typical microUSB cable. Finally, you can download the LPC800 MAX schematic for further examination.
What is mbed anyway?
mbed is a completely online development environment. That is, in a manner very similar to cloud computing services such as Google Docs. However there are some pros and cons of this method. The pros include not having to install any software on the PC – as long as you have a web browser and a USB port you should be fine; any new libraries or IDE updates are handled on the server leaving you to not worry about staying up to date; and the online environment can monitor and update your MCU firmware if necessary.
However the cons are that you cannot work with your code off-line (no working in-flight) and there may be some possible privacy issues. Here’s an example of the environment:
As you can see the IDE is quite straight-forward. All your projects can be found on the left column, the editor in the main window and compiler and other messages in the bottom window. There’s also an online support forum, an official mbed library and user-submitted library database, help files and so on – so there’s plenty of support.
Code is written in C/C++ style and doesn’t present any major hurdles. When it comes time to run the code, the online compiler creates a downloadable binary file which is copied over to the hardware via USB, from which point you reset the board and off it goes.
If you’re using the LPC800-MAX with mbed, be sure to follow the “Getting Started” guide and also check for the latest firmware from the mbed handbook. And although the mbed board appears as a USB storage device, you can still have serial communication with a PC using a virtual serial port via the USB cable connected between the PC and the LPC800-MAX.
Arduino form-factor compatibility
You will notice the header sockets physically match the Arduino Uno R3 specification, so you can drop in an Arduino shield. However the board runs on 3.3V and is 5V-tolerant, so it’s preferable your shields or new designs are good for 3.3V operation. Furthermore, as the onboard LPC812 doesn’t have as much analogue and digital I/O as an ATmega328P found on the Arduino Uno, the extra I/O are provided by two external ICs via I2C. Four analogue inputs are provided by the onboard NXP PCF8591 ADC (and also gives you one DAC as well – convenient) – and the equivalent A4 and A5 pins are not ADC, instead they’re just I2C SDA and SCL respectively.
The extra digital I/O pins are provided via I2C by the aforementioned PCA9672 I/O expander IC. Upon reflection you’d have to be very keen to use a specific Arduino shield as some extra coding would be required to deal with the required I/O – however on the other hand you can easily add external circuitry with blank Arduino protoshields for new projects. Finally, here’s a pin map of the shield connectors.
Not a fan of mbed? Offline tools
NXP have also made their LPCXpressoIDE based on Eclipse available for free download for all platforms - http://lpcware.com/lpcxpresso/download. The free version is good for up to 256 KB code size (provided you register the software) which more than covers the requirements for this and other LPC800 products:
For more information and support, there is a huge repository of information on the NXP website.
Where to get an LPC800-MAX
The board is manufactured and sold by Embedded Artists. At the time of writing the board retails for €15, which is around US$21. NXP also have a range of LPC800 microcontrollers, including very inexpensive through-hole 8-pin versions which are available from the usual retailers. And adafruit of all places have a US$13 starter pack based around the DIP LPC810, which is an interesting 32-bit alternative to the ATtinys out there.
If you’re interested in working with the NXP LPC800-series of microcontrollers, the LPC800-MAX board is a very convenient development board considering the included debugger, Arduino protoshield capability, external GPIO expander and ADC/DAC and onboard LED – as well as the free IDE.
If you enjoy the mbed development environment, the board gives you another hardware option. However if you’re an Arduino user looking for a cheap way of getting a faster board whilst using your existing environment – this is not for you. The product under review was purchased without the knowledge of the supplier.
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