const (
	IO0	= GPIO0
	IO1	= GPIO1
	IO2	= GPIO2
	IO3	= GPIO3
	IO4	= GPIO4
	IO5	= GPIO5
	IO6	= GPIO6
	IO7	= GPIO7
	IO8	= GPIO8
	IO9	= GPIO9
	IO10	= GPIO10
	IO11	= GPIO11
	IO12	= GPIO12
	IO13	= GPIO13
	IO14	= GPIO14
	IO15	= GPIO15
	IO16	= GPIO16
	IO17	= GPIO17
	IO18	= GPIO18
	IO19	= GPIO19
	IO20	= GPIO20
	IO21	= GPIO21

	XTAL_32K_P	= IO0
	XTAL_32K_N	= IO1
	MTMS		= IO4
	MTDI		= IO5
	MTCK		= IO6
	MTDO		= IO7
	VDD_SPI		= IO11
	SPIHD		= IO12
	SPISP		= IO13
	SPICS0		= IO14
	SPID		= IO16
	SPIQ		= IO17
	U0RXD		= IO20
	U0TXD		= IO21

const (
	WS2812 = IO2
const Device = deviceName

Device is the running program’s chip name, such as “ATSAMD51J19A” or “nrf52840”. It is not the same as the CPU name.

The constant is some hardcoded default value if the program does not target a particular chip but instead runs in WebAssembly for example.

const (
	KHz	= 1000
	MHz	= 1000_000
	GHz	= 1000_000_000

Generic constants.

const NoPin = Pin(0xff)

NoPin explicitly indicates “not a pin”. Use this pin if you want to leave one of the pins in a peripheral unconfigured (if supported by the hardware).

const (
	PinOutput	PinMode	= iota
const (
	GPIO0	Pin	= 0
	GPIO1	Pin	= 1
	GPIO2	Pin	= 2
	GPIO3	Pin	= 3
	GPIO4	Pin	= 4
	GPIO5	Pin	= 5
	GPIO6	Pin	= 6
	GPIO7	Pin	= 7
	GPIO8	Pin	= 8
	GPIO9	Pin	= 9
	GPIO10	Pin	= 10
	GPIO11	Pin	= 11
	GPIO12	Pin	= 12
	GPIO13	Pin	= 13
	GPIO14	Pin	= 14
	GPIO15	Pin	= 15
	GPIO16	Pin	= 16
	GPIO17	Pin	= 17
	GPIO18	Pin	= 18
	GPIO19	Pin	= 19
	GPIO20	Pin	= 20
	GPIO21	Pin	= 21
const (
	PinRising	PinChange	= iota + 1

Pin change interrupt constants for SetInterrupt.

const (
	SPI_MODE0	= uint8(0)
	SPI_MODE1	= uint8(1)
	SPI_MODE2	= uint8(2)
	SPI_MODE3	= uint8(3)

	FSPICLK_IN_IDX	= uint32(63)
	FSPICLK_OUT_IDX	= uint32(63)
	FSPIQ_IN_IDX	= uint32(64)
	FSPIQ_OUT_IDX	= uint32(64)
	FSPID_IN_IDX	= uint32(65)
	FSPID_OUT_IDX	= uint32(65)
	FSPIHD_IN_IDX	= uint32(66)
	FSPIHD_OUT_IDX	= uint32(66)
	FSPIWP_IN_IDX	= uint32(67)
	FSPIWP_OUT_IDX	= uint32(67)
	FSPICS0_IN_IDX	= uint32(68)
	FSPICS0_OUT_IDX	= uint32(68)
	FSPICS1_OUT_IDX	= uint32(69)
	FSPICS2_OUT_IDX	= uint32(70)
	FSPICS3_OUT_IDX	= uint32(71)
	FSPICS4_OUT_IDX	= uint32(72)
	FSPICS5_OUT_IDX	= uint32(73)
const (
	// ParityNone means to not use any parity checking. This is
	// the most common setting.
	ParityNone	UARTParity	= iota

	// ParityEven means to expect that the total number of 1 bits sent
	// should be an even number.

	// ParityOdd means to expect that the total number of 1 bits sent
	// should be an odd number.


var (
	ErrTimeoutRNG		= errors.New("machine: RNG Timeout")
	ErrClockRNG		= errors.New("machine: RNG Clock Error")
	ErrSeedRNG		= errors.New("machine: RNG Seed Error")
	ErrInvalidInputPin	= errors.New("machine: invalid input pin")
	ErrInvalidOutputPin	= errors.New("machine: invalid output pin")
	ErrInvalidClockPin	= errors.New("machine: invalid clock pin")
	ErrInvalidDataPin	= errors.New("machine: invalid data pin")
	ErrNoPinChangeChannel	= errors.New("machine: no channel available for pin interrupt")
var (
	DefaultUART	= UART0

	UART0	= &_UART0
	_UART0	= UART{Bus: esp.UART0, Buffer: NewRingBuffer()}
	UART1	= &_UART1
	_UART1	= UART{Bus: esp.UART1, Buffer: NewRingBuffer()}

	onceUart		= sync.Once{}
	errSamePins		= errors.New("UART: invalid pin combination")
	errWrongUART		= errors.New("UART: unsupported UARTn")
	errWrongBitSize		= errors.New("UART: invalid data size")
	errWrongStopBitSize	= errors.New("UART: invalid bit size")
var (
		Bus: esp.USB_DEVICE,

	USBCDC	Serialer	= _USBCDC
var (
	ErrInvalidSPIBus	= errors.New("machine: SPI bus is invalid")
	ErrInvalidSPIMode	= errors.New("machine: SPI mode is invalid")
var (
	// SPI0 and SPI1 are reserved for use by the caching system etc.
	SPI2 = SPI{esp.SPI2}
var (
	ErrPWMPeriodTooLong = errors.New("pwm: period too long")
var Serial = DefaultUART

Serial is implemented via the default (usually the first) UART on the chip.

func CPUFrequency

func CPUFrequency() uint32

CPUFrequency returns the current CPU frequency of the chip. Currently it is a fixed frequency but it may allow changing in the future.

func GetRNG

func GetRNG() (ret uint32, err error)

GetRNG returns 32-bit random numbers using the ESP32-C3 true random number generator, Random numbers are generated based on the thermal noise in the system and the asynchronous clock mismatch. For maximum entropy also make sure that the SAR_ADC is enabled. See esp32-c3_technical_reference_manual_en.pdf p.524

func InitSerial

func InitSerial()

func NewRingBuffer

func NewRingBuffer() *RingBuffer

NewRingBuffer returns a new ring buffer.

type ADC

type ADC struct {
	Pin Pin

type ADCConfig

type ADCConfig struct {
	Reference	uint32	// analog reference voltage (AREF) in millivolts
	Resolution	uint32	// number of bits for a single conversion (e.g., 8, 10, 12)
	Samples		uint32	// number of samples for a single conversion (e.g., 4, 8, 16, 32)
	SampleTime	uint32	// sample time, in microseconds (µs)

ADCConfig holds ADC configuration parameters. If left unspecified, the zero value of each parameter will use the peripheral’s default settings.

type NullSerial

type NullSerial struct {

NullSerial is a serial version of /dev/null (or null router): it drops everything that is written to it.

func (NullSerial) Buffered

func (ns NullSerial) Buffered() int

Buffered returns how many bytes are buffered in the UART. It always returns 0 as there are no bytes to read.

func (NullSerial) Configure

func (ns NullSerial) Configure(config UARTConfig) error

Configure does nothing: the null serial has no configuration.

func (NullSerial) ReadByte

func (ns NullSerial) ReadByte() (byte, error)

ReadByte always returns an error because there aren’t any bytes to read.

func (NullSerial) Write

func (ns NullSerial) Write(p []byte) (n int, err error)

Write is a no-op: none of the data is being written and it will not return an error.

func (NullSerial) WriteByte

func (ns NullSerial) WriteByte(b byte) error

WriteByte is a no-op: the null serial doesn’t write bytes.

type PDMConfig

type PDMConfig struct {
	Stereo	bool
	DIN	Pin
	CLK	Pin

type PWMConfig

type PWMConfig struct {
	// PWM period in nanosecond. Leaving this zero will pick a reasonable period
	// value for use with LEDs.
	// If you want to configure a frequency instead of a period, you can use the
	// following formula to calculate a period from a frequency:
	//     period = 1e9 / frequency
	Period uint64

PWMConfig allows setting some configuration while configuring a PWM peripheral. A zero PWMConfig is ready to use for simple applications such as dimming LEDs.

type Pin

type Pin uint8

Pin is a single pin on a chip, which may be connected to other hardware devices. It can either be used directly as GPIO pin or it can be used in other peripherals like ADC, I2C, etc.

func (Pin) Configure

func (p Pin) Configure(config PinConfig)

Configure this pin with the given configuration.

func (Pin) Get

func (p Pin) Get() bool

Get returns the current value of a GPIO pin when configured as an input or as an output.

func (Pin) High

func (p Pin) High()

High sets this GPIO pin to high, assuming it has been configured as an output pin. It is hardware dependent (and often undefined) what happens if you set a pin to high that is not configured as an output pin.

func (Pin) Low

func (p Pin) Low()

Low sets this GPIO pin to low, assuming it has been configured as an output pin. It is hardware dependent (and often undefined) what happens if you set a pin to low that is not configured as an output pin.

func (Pin) PortMaskClear

func (p Pin) PortMaskClear() (*uint32, uint32)

Return the register and mask to disable a given GPIO pin. This can be used to implement bit-banged drivers.

Warning: only use this on an output pin!

func (Pin) PortMaskSet

func (p Pin) PortMaskSet() (*uint32, uint32)

Return the register and mask to enable a given GPIO pin. This can be used to implement bit-banged drivers.

Warning: only use this on an output pin!

func (Pin) Set

func (p Pin) Set(value bool)

Set the pin to high or low. Warning: only use this on an output pin!

func (Pin) SetInterrupt

func (p Pin) SetInterrupt(change PinChange, callback func(Pin)) (err error)

SetInterrupt sets an interrupt to be executed when a particular pin changes state. The pin should already be configured as an input, including a pull up or down if no external pull is provided.

You can pass a nil func to unset the pin change interrupt. If you do so, the change parameter is ignored and can be set to any value (such as 0). If the pin is already configured with a callback, you must first unset this pins interrupt before you can set a new callback.

type PinChange

type PinChange uint8

type PinConfig

type PinConfig struct {
	Mode PinMode

type PinMode

type PinMode uint8

PinMode sets the direction and pull mode of the pin. For example, PinOutput sets the pin as an output and PinInputPullup sets the pin as an input with a pull-up.

type RingBuffer

type RingBuffer struct {
	rxbuffer	[bufferSize]volatile.Register8
	head		volatile.Register8
	tail		volatile.Register8

RingBuffer is ring buffer implementation inspired by post at https://www.embeddedrelated.com/showthread/comp.arch.embedded/77084-1.php

func (*RingBuffer) Clear

func (rb *RingBuffer) Clear()

Clear resets the head and tail pointer to zero.

func (*RingBuffer) Get

func (rb *RingBuffer) Get() (byte, bool)

Get returns a byte from the buffer. If the buffer is empty, the method will return a false as the second value.

func (*RingBuffer) Put

func (rb *RingBuffer) Put(val byte) bool

Put stores a byte in the buffer. If the buffer is already full, the method will return false.

func (*RingBuffer) Used

func (rb *RingBuffer) Used() uint8

Used returns how many bytes in buffer have been used.

type SPI

type SPI struct {
	Bus *esp.SPI2_Type

Serial Peripheral Interface on the ESP32-C3.

func (SPI) Configure

func (spi SPI) Configure(config SPIConfig) error

Configure and make the SPI peripheral ready to use.

func (SPI) Transfer

func (spi SPI) Transfer(w byte) (byte, error)

Transfer writes/reads a single byte using the SPI interface. If you need to transfer larger amounts of data, Tx will be faster.

func (SPI) Tx

func (spi SPI) Tx(w, r []byte) error

Tx handles read/write operation for SPI interface. Since SPI is a syncronous write/read interface, there must always be the same number of bytes written as bytes read. This is accomplished by sending zero bits if r is bigger than w or discarding the incoming data if w is bigger than r.

type SPIConfig

type SPIConfig struct {
	Frequency	uint32
	SCK		Pin	// Serial Clock
	SDO		Pin	// Serial Data Out (MOSI)
	SDI		Pin	// Serial Data In  (MISO)
	CS		Pin	// Chip Select (optional)
	LSBFirst	bool	// MSB is default
	Mode		uint8	// SPI_MODE0 is default

SPIConfig is used to store config info for SPI.

type Serialer

type Serialer interface {
	WriteByte(c byte) error
	Write(data []byte) (n int, err error)
	Configure(config UARTConfig) error
	Buffered() int
	ReadByte() (byte, error)
	DTR() bool
	RTS() bool

type UART

type UART struct {
	Bus			*esp.UART_Type
	Buffer			*RingBuffer
	ParityErrorDetected	bool	// set when parity error detected
	DataErrorDetected	bool	// set when data corruption detected
	DataOverflowDetected	bool	// set when data overflow detected in UART FIFO buffer or RingBuffer

func (*UART) Buffered

func (uart *UART) Buffered() int

Buffered returns the number of bytes currently stored in the RX buffer.

func (*UART) Configure

func (uart *UART) Configure(config UARTConfig) error

func (*UART) Read

func (uart *UART) Read(data []byte) (n int, err error)

Read from the RX buffer.

func (*UART) ReadByte

func (uart *UART) ReadByte() (byte, error)

ReadByte reads a single byte from the RX buffer. If there is no data in the buffer, returns an error.

func (*UART) Receive

func (uart *UART) Receive(data byte)

Receive handles adding data to the UART’s data buffer. Usually called by the IRQ handler for a machine.

func (*UART) SetBaudRate

func (uart *UART) SetBaudRate(baudRate uint32)

func (*UART) SetFormat

func (uart *UART) SetFormat(dataBits, stopBits int, parity UARTParity) error

func (*UART) Write

func (uart *UART) Write(data []byte) (n int, err error)

Write data over the UART’s Tx. This function blocks until the data is finished being sent.

func (*UART) WriteByte

func (uart *UART) WriteByte(c byte) error

WriteByte writes a byte of data over the UART’s Tx. This function blocks until the data is finished being sent.

type UARTConfig

type UARTConfig struct {
	BaudRate	uint32
	TX		Pin
	RX		Pin
	RTS		Pin
	CTS		Pin

UARTConfig is a struct with which a UART (or similar object) can be configured. The baud rate is usually respected, but TX and RX may be ignored depending on the chip and the type of object.

type UARTParity

type UARTParity uint8

UARTParity is the parity setting to be used for UART communication.


type USB_DEVICE struct {
	Bus *esp.USB_DEVICE_Type

USB Serial/JTAG Controller See esp32-c3_technical_reference_manual_en.pdf pg. 736

func (*USB_DEVICE) Buffered

func (usbdev *USB_DEVICE) Buffered() int

func (*USB_DEVICE) Configure

func (usbdev *USB_DEVICE) Configure(config UARTConfig) error


func (usbdev *USB_DEVICE) DTR() bool


func (usbdev *USB_DEVICE) RTS() bool

func (*USB_DEVICE) ReadByte

func (usbdev *USB_DEVICE) ReadByte() (byte, error)

func (*USB_DEVICE) Write

func (usbdev *USB_DEVICE) Write(data []byte) (n int, err error)

func (*USB_DEVICE) WriteByte

func (usbdev *USB_DEVICE) WriteByte(c byte) error
Last modified April 17, 2024: Fix doc-gen and update docs (8a74a2b)