In WVariant.h the following is missing at line 200 inside the _ETCChannel enumerated type: #if defined(__SAMD21J18A__) TC6_CH0 = (6<<8)|(0), TC6_CH1 = (6<<8)|(1), TC7_CH0 = (7<<8)|(0), TC7_CH1 = (7<<8)|(1), #endif // __SAMD21J18A__