Lowering consumption, Part 2: Software

Measurement setup

• Yamaha board V1, with only the Arduino Pro Mini and the RECOM 0.5A 3.3V installed.
• Supplied from a 42V battery
• Multimeter in line to measure current
• 100 Ohm series resistance on battery to act as a shunt to measure current w/ scope
• Scope probe on shunt
• Scope probe on UART output to verify operation

Result

• 540 uA awake
• 190 uA in powerDowN
• 300 uA average power consumption
• Even the small ripple of waking up and going back to power down is visible on the scope!!
• Lotsa noise, had to estimate an average current with the cursors
• The Biltema multimeter is not fast enough to track the current - is oscillates 250 uA to 405 uA

Fixing the LEDs

Now they are on interrupt!

Averaging

I want to average the five highest samples of the last 5 minutes. 5 minutes is 300 seconds, that will be 1200 cycles. If I want to have only 20 samples in 5 minutes, I need to take a sample each 60th cycle.