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.
Think in assembly, write in C. Sent from a bunker in an undisclosed location deep beneath a mountain.