Port mapping:

ArduinoPWMPIN5V tolerantFunctions
A0-A5-PA1-PA63.3V onlyADC
D0YesPC2YesRXD0
D1YesPC3YesTXD0
D2YesPC0YesSDA
D3YesPC1YesSCL
D4YesPD2YesRXD2
D5YesPD3YesTXD2
D6YesPD4Yes
D7-PB2YesDAC
D8-PB3YesDAC
D9YesPC4Yes
D10YesPC5Yes
D11YesPD5YesMOSI
D12-PD6YesMISO/RXD3
D13-PD7YesSCK/TXD3
D14YesPE0YesSDA11
D15YesPE1YesSCL11
D16YesPE2YesRXD4
D17YesPE3YesTXD4
D18YesPD0Yes
D19YesPD1Yes
D20-PC6YesRXD1
D21-PC7YesTXD1

1 this was incorrectly specified as port D18/D19 on the first revision of the board

Schematic:

[PDF]

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