The Buckymeter is basically a modified MCB2130 evaluation board (see Photo 2). For testing purposes, I transferred the circuit to a custom PCB featuring a Philips LPC2138 microcontroller, a pair of Analog Devices ADXL210 ±10-g dual-axis accelerometers, and additional support circuitry. The Buckymeter connects to the bucking dummy via off-board optoisolators.

The CPU is an LPC2138 in an LQFP64 package. It’s wired in accordance with the schematic that came with the MCB2130 evaluation board. In addition to 32 KB of RAM for data buffering and plenty of I/O pins, several key features make the LPC2138 ideal for this system. Four timer capture inputs make it easy to connect to the required accelerometers. Dual UARTs allow for concurrent wired and wireless access to the Buckymeter’s internal data.

The 512 KB of run-time programmable flash memory enables me to store data from more than 20 bulls. The SPI provides developmental access to expanded EEPROM storage. I use the built-in serial bootloader for development programming. The 16/32-bit ARM core can be used at 60 MHz for built-in advanced data processing.

The only disadvantage to using this CPU is the vector interrupt controller (VIC). The VIC provides a huge amount of flexibility, but it requires a complicated setup. It’s particularly difficult to create a set of nested interrupts to wait for the completion of data acquisition.