Extend STM mbed board. Thanks Y.Kuroda-san for creating good function.

Dependencies:   RingBuffer

Dependents:   Frequency_Counter_w_GPS_1PPS FreqCntr_GPS1PPS_F746F4xx_w_recipro

Fork of iSerial by Yoji KURODA

Revision:
11:6bea021727a1
Parent:
9:45be5c5d5101