Datasheet


WARNING
Using IOVDD voltages greater than 1.8V, with the input thresholds set for 1.8V may result in damage to the chip.
Pad input threshold are adjusted on a per bank basis, with separate VOLTAGE_SELECT registers for the pads associated with
the User IO bank (IO Bank 0) and the QSPI IO bank. However, both banks share the same digital IO supply (IOVDD), so
both register should always be set to the same value.
Pad register details are available in Section 2.19.6.3, “Pad Control - User Bank” and Section 2.19.6.4, “Pad Control - QSPI
Bank”.
2.19.5. Software Examples
2.19.5.1. Select an IO function
An IO pin can perform many different functions and must be configured before use. For example, you may want it to be
a UART_TX pin, or a PWM output. The SDK provides gpio_set_function for this purpose. Many SDK examples will call
gpio_set_function at the beginning so that it can print to a UART.
The SDK starts by defining a structure to represent the registers of IO bank 0, the User IO bank. Each IO has a status
register, followed by a control register. There are 30 IOs, so the structure containing a status and control register is
instantiated as io[30] to repeat it 30 times.
SDK: https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2040/hardware_structs/include/hardware/structs/iobank0.h Lines 21 - 30
21 typedef struct {
22 struct {
23 io_rw_32 status;
24 io_rw_32 ctrl;
25 } io[30];
26 io_rw_32 intr[4];
27 io_irq_ctrl_hw_t proc0_irq_ctrl;
28 io_irq_ctrl_hw_t proc1_irq_ctrl;
29 io_irq_ctrl_hw_t dormant_wake_irq_ctrl;
30 } iobank0_hw_t;
A similar structure is defined for the pad control registers for IO bank 1. By default, all pads come out of reset ready to
use, with their input enabled and output disable set to 0. Regardless, gpio_set_function in the SDK sets these to make
sure the pad is ready to use by the selected function. Finally, the desired function select is written to the IO control
register (see GPIO0_CTRL for an example of an IO control register).
SDK: https://github.com/raspberrypi/pico-sdk/tree/master/src/rp2_common/hardware_gpio/gpio.c Lines 28 - 41
28 // Select function for this GPIO, and ensure input/output are enabled at the pad.
29 // This also clears the input/output/irq override bits.
30 void gpio_set_function(uint gpio, enum gpio_function fn) {
31 invalid_params_if(GPIO, gpio >= NUM_BANK0_GPIOS);
32 invalid_params_if(GPIO, ((uint32_t)fn << IO_BANK0_GPIO0_CTRL_FUNCSEL_LSB) &
Ê ~IO_BANK0_GPIO0_CTRL_FUNCSEL_BITS);
33 // Set input enable on, output disable off
34 hw_write_masked(&padsbank0_hw->io[gpio],
35 PADS_BANK0_GPIO0_IE_BITS,
36 PADS_BANK0_GPIO0_IE_BITS | PADS_BANK0_GPIO0_OD_BITS
37 );
38 // Zero all fields apart from fsel; we want this IO to do what the peripheral tells it.
39 // This doesn't affect e.g. pullup/pulldown, as these are in pad controls.
40 iobank0_hw->io[gpio].ctrl = fn << IO_BANK0_GPIO0_CTRL_FUNCSEL_LSB;
RP2040 Datasheet
2.19. GPIO 262