The maximum clock frequency that can be achieved with the internal oscillator is 25 MHz. However, it's recommended to use an external crystal oscillator for frequencies above 12 MHz for better accuracy and stability.
To configure the USB interface to work in device mode, you need to set the USB_MODE pin high, enable the USB clock, and configure the USB registers accordingly. You can refer to the USB chapter in the user manual for more details.
The maximum amount of current that can be sourced or sunk by the GPIO pins is 4 mA. However, it's recommended to limit the current to 2 mA or less to ensure reliable operation and prevent overheating.
To use the ADC in differential mode, you need to configure the ADC registers to select the differential input channels, and set the ADC mode to differential. You also need to ensure that the input signals are within the specified common-mode voltage range.
The minimum voltage range for the ADC inputs is 0 V, and the maximum voltage range is VCC (typically 3.3 V or 5 V). However, the recommended input voltage range is 0 V to VCC - 1.5 V to ensure accurate conversions.