General Purpose Input Output

4. General Purpose Input Output#

GPIOs are nothing but digital input/output pins, the state of which can be controlled directly by the software running on the processors, or by a number of other peripherals available in the μC. As discussed in previous chapters, the RP2040 μC has 30 GPIOs, out of which 4 can also be used as inputs to the chip’s Analogue to Digital Converter (ADC). Each GPIO in RP2040 can perform a specific function of a specific peripheral. Following table lists the function that each GPIO can perform for each peripheral that we may discuss throughout this course. Full table is available here.

GPIO\Func	1	2	3	4	5
0	SPI0 RX	UART0 TX	I2C0 SDA	PWM0 A	SIO
1	SPI0 CSn	UART0 RX	I2C0 SCL	PWM0 B	SIO
2	SPI0 SCK	UART0 CTS	I2C1 SDA	PWM1 A	SIO
3	SPI0 TX	UART0 RTS	I2C1 SCL	PWM1 B	SIO
4	SPI0 RX	UART1 TX	I2C0 SDA	PWM2 A	SIO
5	SPI0 CSn	UART1 RX	I2C0 SCL	PWM2 B	SIO
6	SPI0 SCK	UART1 CTS	I2C1 SDA	PWM3 A	SIO
7	SPI0 TX	UART1 RTS	I2C1 SCL	PWM3 B	SIO
8	SPI1 RX	UART1 TX	I2C0 SDA	PWM4 A	SIO
9	SPI1 CSn	UART1 RX	I2C0 SCL	PWM4 B	SIO
10	SPI1 SCK	UART1 CTS	I2C1 SDA	PWM5 A	SIO
11	SPI1 TX	UART1 RTS	I2C1 SCL	PWM5 B	SIO
12	SPI1 RX	UART0 TX	I2C0 SDA	PWM6 A	SIO
13	SPI1 CSn	UART0 RX	I2C0 SCL	PWM6 B	SIO
14	SPI1 SCK	UART0 CTS	I2C1 SDA	PWM7 A	SIO
15	SPI1 TX	UART0 RTS	I2C1 SCL	PWM7 B	SIO
16	SPI0 RX	UART0 TX	I2C0 SDA	PWM0 A	SIO
17	SPI0 CSn	UART0 RX	I2C0 SCL	PWM0 B	SIO
18	SPI0 SCK	UART0 CTS	I2C1 SDA	PWM1 A	SIO
19	SPI0 TX	UART0 RTS	I2C1 SCL	PWM1 B	SIO
20	SPI0 RX	UART1 TX	I2C0 SDA	PWM2 A	SIO
21	SPI0 CSn	UART1 RX	I2C0 SCL	PWM2 B	SIO
22	SPI0 SCK	UART1 CTS	I2C1 SDA	PWM3 A	SIO
23	SPI0 TX	UART1 RTS	I2C1 SCL	PWM3 B	SIO
24	SPI1 RX	UART1 TX	I2C0 SDA	PWM4 A	SIO
25	SPI1 CSn	UART1 RX	I2C0 SCL	PWM4 B	SIO
26	SPI1 SCK	UART1 CTS	I2C1 SDA	PWM5 A	SIO
27	SPI1 TX	UART1 RTS	I2C1 SCL	PWM5B	SIO
28	SPI1 RX	UART0 TX	I2C0 SDA	PWM6 A	SIO
29	SPI1 CSn	UART0 RX	I2C0 SCL	PWM6 B	SIO

The actual working of a GPIO pin requires understanding of how a transistor works. Thus, this chapter will attempt to explain working of a GPIO in a much simpler way. However, keep in mind that this simplified explanation is not really true.