1. pwm led : setled(led0-3, period[-128-127], percent[0-100], repeats)
period : 1-127 :  1/1-1/127 s,
(-2 - -128) : 2 - 128 s
2. BM57 P07 RX_IND, GPA15 : pull high to disable rx indicator,
othewise bt module won't enter low power mode. If there is big data,
pull low this pin to prevent entering lower power mode.
average power of BT, 1.6ma-2.xma