The orientation of the board is seen as the Micro-USB being at the top.
|J2, bottom pin
|Interrupt, I2C1_SDA, USART1_RX
|J2, left pin
|J2, right, top pin
|Interrupt, I2C1_SCL, USART1_TX
|PIR, left, top pin
|PIR, right, top pin
|PIR, left, bottom pin
|Interrupt, ADC3, USART2_RX
|PIR, right, bottom pin
Note: Keep in mind when using I2C on these pins that the internal senors are utilizing the same bus with different GPIO pins (PB8-I2C1_SCL/PB9-I2C1_SDA). Trying to use the same bus on different pins at the same time might cause issues during initialization.
This is a view from the bottom of the board. The pin names are also displayed on the silk screen of the board.