modes

hold run button at power on

Fun1 - dc load (continue working on voltage alarm)
Fun2 - battery test (stop load at specified voltage)8n

serial

115200 8n1

pins from bottom of the board upwards

G - GND
R - RX
T - TX
L - always low?
F - 50 Khz quare wave
Vc - input voltage

3 byte output, first two bytes are BCD voltage (3.35V) and last one is status (1=ok, 0=under voltage alarm)

pi@rpi2 ~ $ microcom -s 115200 -p /dev/ttyUSB4 | od -An -t x1 -w3
 04 35 01
*
 04 36 01
 04 35 01
*
 04 36 01
*
 04 35 01
*
 04 36 01
 04 35 01