Variant.cpp file for RedBoard Turbo needs additional PinDescription entries in g_APinDescription array for FLASH_MISO (PB03) . There does not currently appear to be an entry for PORTB pin 3 (PB03) in the g_APinDescription array. I believe the entry should be as follows:
Yes quite odd that it didn't make it into the pin description list. I have simply added it to the end and you'll just have to reassign the SERCOM port in your sketch to use SPI with the flash.
Variant.cpp file for RedBoard Turbo needs additional PinDescription entries in g_APinDescription array for FLASH_MISO (PB03) . There does not currently appear to be an entry for PORTB pin 3 (PB03) in the g_APinDescription array. I believe the entry should be as follows:
{ PORTB, 3, PIO_SERCOM_ALT, PIN_ATTR_NONE, No_ADC_Channel, NOT_ON_PWM, NOT_ON_TIMER, EXTERNAL_INT_NONE }
FLASH_MOSI (PB22) and FLASH_SCK (PB23) already have entries in g_APinDescription.