I have designed a new development board which is supposed to be used in many of the projects I am/will be involved in. It’s been built around an NXP LPC2138 microcontroller which has the following main features:
- 16/32 bit ARM7TDMI-S microcontroller (LQFP64 package)
- 32 KB of internal SRAM and 512 KB of on-chip flash program memory. 128-bit wide interface/accelerator enables high-speed 60 Mhz operation.
- In-System Programming/In-Application Programming (ISP/IAP) via on-chip bootloader software. Single flash sector or full chip erase in 400 ms and programming of 256 B in 1 ms.
- Two 8-channel 10-bit ADCs with conversion times as low as 2.44 us per channel.
- Two 32-bit timers/external event counters (with four capture and four compare channels each), PWM unit (six outputs) and watchdog.
- Multiple serial interfaces including two UARTs (16C550), two Fast I2C-bus (400 kbit/s), SPI and SSP with buffering and variable data length capabilities.
- Vectored interrupt controller with configurable priorities and vector addresses.
- Up to forty-seven 5 V tolerant general purpose I/O pins in tiny LQFP64 package.
- Up to nine edge or level sensitive external interrupt pins available.
- 60 MHz maximum CPU clock available from programmable on-chip PLL with settling time of 100 us.
- On-chip integrated oscillator operates with external crystal in range of 1 MHz to 30 MHz and with external oscillator up to 50 MHz.
- Power saving modes include Idle and Power-down.
- Individual enable/disable of peripheral functions as well as peripheral clock scaling down for additional power optimization.
- Processor wake-up from Power-down mode via external interrupt or BOD.
- Single power supply chip with POR and BOD circuits:
- CPU operating voltage range of 3.0 V to 3.6 V (3.3 V +- 10 pct) with 5 V tolerant I/O pads.
This microcontroller is suitable for most of my projects due to its high processing power (up to 60 MIPS) and its large amount of memory. Also, the board itself has some kind of features that I couldn’t find in any other development board:
- Audio playing support with earphones connector. Connected to the DAC output of the microcontroller through an audio amplifier circuit. It is possible to use the DAC output for another purposes.
- Audio recording support with microphone connector. Connected to one of the ADCs channels of the microcontroller through an audio amplifier and signal conditioning circuit. It is possible to use the ADC input for another purposes.
- Selectable power supply input: directly from USB or from external battery for standalone applications (Vin ranging from 3.3V to 20V).
- RS232 interface through DB9 connector.
- USB communication through USB Type-B connector (on-board USB-Serial converter). RX and TX leds.
- 8 General Purpose LED’s connected to the microcontroller through an output buffer which can be disabled through a jumper in case that these GPIO pins are needed.
- Reset Button
- General purpose button connected to one of the external interrupts of the microcontroller.
- In Circuit Programming interface up to 115200 bps.
- 12 MHz crystal for operation up to 60 MHz.
- MMC/SD memory card interface connected to the SPI bus of the microcontroller.
- Integrated Li-Ion / Li-Po Battery charger. It can charge batteries from USB or external power supply with LED charge indicators.
- All the GPIO pins are available in the board. Including JTAG interface for programming / debugging in circuit.
- Battery level monitoring. The input voltage is connected to one of the ADC inputs of the microcontroller through a voltage divisor so that it can be measured by software.
As the ARM architecture is being more and more popular there are lots of development tools available for all the platforms.
On Windows machines you can use WinARM which is a collection of tools to develop software for the ARM-family of controllers/processors including GNU C/C++ compiler (gcc / g++), GNU Binutils, GDB server, …
Most of these tools are part of GNU arm-elf toolchain distributions so you can easily develop /program the LPC2138 microcontroller under GNU/Linux.
Also, you can find some good commercial software for ARM microcontrollers/microprocessors like the ARM RealView Development Suite.
In some applications an RTOS (Real Time Operating System) is needed and there are some of them available for this microcontroller. I would stand out the following ones: FreeRTOS (free for non-commercial purposes) and RealView RL-ARM.