This is a simple voltage and current meter that uses the TI INA219 chip. Voltage measurement range is 0 to 26 volts with 4 mV resolution and current measurement range is -4 to +4 amps with 1 mV resolution (when using a 0.01 ohm shunt). The specs are inferior to a pair of quality multimeters, but it is a fraction of the price and shows wattage in addition to voltage and current. The Nokia 5110 display is used so the firmware could be enhanced to do simple graphing. Sending the measurements to a computer could also be done.
Using the INA219 makes for a very simple circuit.
The normal display is three lines with voltage, amperage and wattage.
Pressing the P1.3 switch will show the 6 registers in the INA219 in hex and signed decimal.
The code is written in C++ and uses templates for the LCD, IIC and INA219. Software SPI and IIC is used for maximum portability.
In common with other microcontroller vendors, TI has developed a two-wire debugging interface found on some of their MSP430 parts that can replace the larger JTAG interface. The eZ430 Development Tool contains a full USB-connected Flash Emulation Tool ("FET") for this new two-wire protocol, named "Spy-Bi-Wire" by TI. Spy-Bi-Wire was initially introduced on only the smallest devices in the 'F2xx family with limited number of I/O pins, such as the MSP430F20xx, MSP430F21x2, and MSP430F22x2. The support for Spy-Bi-Wire has been expanded with the introduction of the latest '5xx family, where all devices have support Spy-Bi-Wire interface in addition to JTAG.
The advantage of the Spy-Bi-Wire protocol is that it uses only two communication lines, one of which is the dedicated _RESET line. The JTAG interface on the lower pin count MSP430 parts is multiplexed with general purpose I/O lines. This makes it relatively difficult to debug circuits built around the small, low-I/O-budget chips, since the full 4-pin JTAG hardware will conflict with anything else connected to those I/O lines. This problem is alleviated with the Spy-Bi-Wire-capable chips, which are still compatible with the normal JTAG interface for backwards compatibility with the old development tools.
Take a look at this thread for a technical discussion on the topic.