x9pro

Constants

const (
	LED		Pin	= 4	// HR LED pin
	UART_TX_PIN	Pin	= NoPin
	UART_RX_PIN	Pin	= NoPin
	SCL_PIN		Pin	= NoPin
	SDA_PIN		Pin	= NoPin
	SPI0_SCK_PIN	Pin	= 18
	SPI0_SDI_PIN	Pin	= 19
	SPI0_SDO_PIN	Pin	= 20
)

https://hackaday.io/project/144350-hacking-wearables-for-mental-health-and-more/details

const (
	OLED_CS		Pin	= 15	// chip select
	OLED_RES	Pin	= 14	// reset pin
	OLED_DC		Pin	= 13	// data/command
	OLED_SCK	Pin	= 12	// SPI clock
	OLED_SDO	Pin	= 11	// SPI SDO (chip-out, peripheral-in)
	OLED_LED_POW	Pin	= 16
	OLED_IC_POW	Pin	= 17
)

LCD pins.

const HasLowFrequencyCrystal = true
const (
	TWI_FREQ_100KHZ	= 100000
	TWI_FREQ_400KHZ	= 400000
)

TWI_FREQ is the I2C bus speed. Normally either 100 kHz, or 400 kHz for high-speed bus.

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 (
	PinInput		PinMode	= (nrf.GPIO_PIN_CNF_DIR_Input << nrf.GPIO_PIN_CNF_DIR_Pos) | (nrf.GPIO_PIN_CNF_INPUT_Connect << nrf.GPIO_PIN_CNF_INPUT_Pos)
	PinInputPullup		PinMode	= PinInput | (nrf.GPIO_PIN_CNF_PULL_Pullup << nrf.GPIO_PIN_CNF_PULL_Pos)
	PinInputPulldown	PinMode	= PinInput | (nrf.GPIO_PIN_CNF_PULL_Pulldown << nrf.GPIO_PIN_CNF_PULL_Pos)
	PinOutput		PinMode	= (nrf.GPIO_PIN_CNF_DIR_Output << nrf.GPIO_PIN_CNF_DIR_Pos) | (nrf.GPIO_PIN_CNF_INPUT_Disconnect << nrf.GPIO_PIN_CNF_INPUT_Pos)
)
const (
	PinRising	PinChange	= nrf.GPIOTE_CONFIG_POLARITY_LoToHi
	PinFalling	PinChange	= nrf.GPIOTE_CONFIG_POLARITY_HiToLo
	PinToggle	PinChange	= nrf.GPIOTE_CONFIG_POLARITY_Toggle
)

Pin change interrupt constants for SetInterrupt.

const (
	P0_00	Pin	= 0
	P0_01	Pin	= 1
	P0_02	Pin	= 2
	P0_03	Pin	= 3
	P0_04	Pin	= 4
	P0_05	Pin	= 5
	P0_06	Pin	= 6
	P0_07	Pin	= 7
	P0_08	Pin	= 8
	P0_09	Pin	= 9
	P0_10	Pin	= 10
	P0_11	Pin	= 11
	P0_12	Pin	= 12
	P0_13	Pin	= 13
	P0_14	Pin	= 14
	P0_15	Pin	= 15
	P0_16	Pin	= 16
	P0_17	Pin	= 17
	P0_18	Pin	= 18
	P0_19	Pin	= 19
	P0_20	Pin	= 20
	P0_21	Pin	= 21
	P0_22	Pin	= 22
	P0_23	Pin	= 23
	P0_24	Pin	= 24
	P0_25	Pin	= 25
	P0_26	Pin	= 26
	P0_27	Pin	= 27
	P0_28	Pin	= 28
	P0_29	Pin	= 29
	P0_30	Pin	= 30
	P0_31	Pin	= 31
)

Hardware pins

const (
	// ParityNone means to not use any parity checking. This is
	// the most common setting.
	ParityNone	UARTParity	= 0

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

	// ParityOdd means to expect that the total number of 1 bits sent
	// should be an odd number.
	ParityOdd	UARTParity	= 2
)

Variables

var DefaultUART = UART0
var (
	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 (
	ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
)
var (
	// UART0 is the hardware UART on the NRF SoC.
	_UART0	= UART{Buffer: NewRingBuffer()}
	UART0	= &_UART0
)

UART

var (
	I2C0	= (*I2C)(unsafe.Pointer(nrf.TWI0))
	I2C1	= (*I2C)(unsafe.Pointer(nrf.TWI1))
)

There are 2 I2C interfaces on the NRF.

var (
	PWM0	= &PWM{PWM: nrf.PWM0}
	PWM1	= &PWM{PWM: nrf.PWM1}
	PWM2	= &PWM{PWM: nrf.PWM2}
)

PWM

var (
	SPI0	= SPI{Bus: nrf.SPIM0, buf: new([1]byte)}
	SPI1	= SPI{Bus: nrf.SPIM1, buf: new([1]byte)}
	SPI2	= SPI{Bus: nrf.SPIM2, buf: new([1]byte)}
)

There are 3 SPI interfaces on the NRF528xx.

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

func InitADC

func InitADC()

InitADC initializes the registers needed for ADC.

func NewRingBuffer

func NewRingBuffer() *RingBuffer

NewRingBuffer returns a new ring buffer.

type ADC

type ADC struct {
	Pin Pin
}

func (ADC) Configure

func (a ADC) Configure(ADCConfig)

Configure configures an ADC pin to be able to read analog data.

func (ADC) Get

func (a ADC) Get() uint16

Get returns the current value of a ADC pin in the range 0..0xffff.

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)
}

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

type I2C

type I2C struct {
	Bus nrf.TWI_Type
}

I2C on the NRF.

func (*I2C) Configure

func (i2c *I2C) Configure(config I2CConfig) error

Configure is intended to setup the I2C interface.

func (*I2C) ReadRegister

func (i2c *I2C) ReadRegister(address uint8, register uint8, data []byte) error

ReadRegister transmits the register, restarts the connection as a read operation, and reads the response.

Many I2C-compatible devices are organized in terms of registers. This method is a shortcut to easily read such registers. Also, it only works for devices with 7-bit addresses, which is the vast majority.

func (*I2C) Tx

func (i2c *I2C) Tx(addr uint16, w, r []byte) (err error)

Tx does a single I2C transaction at the specified address. It clocks out the given address, writes the bytes in w, reads back len(r) bytes and stores them in r, and generates a stop condition on the bus.

func (*I2C) WriteRegister

func (i2c *I2C) WriteRegister(address uint8, register uint8, data []byte) error

WriteRegister transmits first the register and then the data to the peripheral device.

Many I2C-compatible devices are organized in terms of registers. This method is a shortcut to easily write to such registers. Also, it only works for devices with 7-bit addresses, which is the vast majority.

type I2CConfig

type I2CConfig struct {
	Frequency	uint32
	SCL		Pin
	SDA		Pin
}

I2CConfig is used to store config info for I2C.

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 PWM

type PWM struct {
	PWM	*nrf.PWM_Type

	channelValues	[4]volatile.Register16
}

PWM is one PWM peripheral, which consists of a counter and multiple output channels (that can be connected to actual pins). You can set the frequency using SetPeriod, but only for all the channels in this PWM peripheral at once.

func (*PWM) Channel

func (pwm *PWM) Channel(pin Pin) (uint8, error)

Channel returns a PWM channel for the given pin.

func (*PWM) Configure

func (pwm *PWM) Configure(config PWMConfig) error

Configure enables and configures this PWM. On the nRF52 series, the maximum period is around 0.26s.

func (*PWM) Set

func (pwm *PWM) Set(channel uint8, value uint32)

Set updates the channel value. This is used to control the channel duty cycle. For example, to set it to a 25% duty cycle, use:

ch.Set(ch.Top() / 4)

ch.Set(0) will set the output to low and ch.Set(ch.Top()) will set the output to high, assuming the output isn’t inverted.

func (*PWM) SetInverting

func (pwm *PWM) SetInverting(channel uint8, inverting bool)

SetInverting sets whether to invert the output of this channel. Without inverting, a 25% duty cycle would mean the output is high for 25% of the time and low for the rest. Inverting flips the output as if a NOT gate was placed at the output, meaning that the output would be 25% low and 75% high with a duty cycle of 25%.

func (*PWM) SetPeriod

func (pwm *PWM) SetPeriod(period uint64) error

SetPeriod updates the period of this PWM peripheral. To set a particular frequency, use the following formula:

period = 1e9 / frequency

If you use a period of 0, a period that works well for LEDs will be picked.

SetPeriod will not change the prescaler, but also won’t change the current value in any of the channels. This means that you may need to update the value for the particular channel.

Note that you cannot pick any arbitrary period after the PWM peripheral has been configured. If you want to switch between frequencies, pick the lowest frequency (longest period) once when calling Configure and adjust the frequency here as needed.

func (*PWM) Top

func (pwm *PWM) Top() uint32

Top returns the current counter top, for use in duty cycle calculation. It will only change with a call to Configure or SetPeriod, otherwise it is constant.

The value returned here is hardware dependent. In general, it’s best to treat it as an opaque value that can be divided by some number and passed to pwm.Set (see pwm.Set for more information).

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.

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 port. This can be used to implement bit-banged drivers.

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.

func (Pin) Set

func (p Pin) Set(high 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)) 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.

This call will replace a previously set callback on this pin. 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).

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	*nrf.SPIM_Type
	buf	*[1]byte	// 1-byte buffer for the Transfer method
}

SPI on the NRF.

func (SPI) Configure

func (spi SPI) Configure(config SPIConfig)

Configure is intended to setup the SPI interface.

func (SPI) Transfer

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

Transfer writes/reads a single byte using the SPI interface.

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. Therefore, if the number of bytes don’t match it will be padded until they fit: if len(w) > len(r) the extra bytes received will be dropped and if len(w) < len(r) extra 0 bytes will be sent.

type SPIConfig

type SPIConfig struct {
	Frequency	uint32
	SCK		Pin
	SDO		Pin
	SDI		Pin
	LSBFirst	bool
	Mode		uint8
}

SPIConfig is used to store config info for SPI.

type UART

type UART struct {
	Buffer *RingBuffer
}

UART on the NRF.

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)

Configure the UART.

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(br uint32)

SetBaudRate sets the communication speed for the UART.

func (*UART) Write

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

Write data to the UART.

func (*UART) WriteByte

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

WriteByte writes a byte of data to the UART.

type UARTConfig

type UARTConfig struct {
	BaudRate	uint32
	TX		Pin
	RX		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 int

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