digispark
Constants
const (
P0 Pin = PB0 // PWM available (Timer0 OC0A)
P1 Pin = PB1 // PWM available (Timer0 OC0B or Timer1 OC1A)
P2 Pin = PB2
P3 Pin = PB3
P4 Pin = PB4 // PWM available (Timer1 OC1B)
P5 Pin = PB5
LED = P1
)
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 (
PB0 Pin = iota
PB1
PB2
PB3
PB4
PB5
)
const (
PinInput PinMode = iota
PinInputPullup
PinOutput
)
const (
Mode0 = 0
Mode1 = 1
Mode2 = 2
Mode3 = 3
)
SPI phase and polarity configs CPOL and CPHA
Variables
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 (
Timer0 = PWM{0} // 8 bit timer for PB0 and PB1
Timer1 = PWM{1} // 8 bit high-speed timer for PB1 and PB4
)
var SPI0 = SPI{}
SPI0 is the USI-based SPI interface on the ATTiny85
var (
ErrPWMPeriodTooLong = errors.New("pwm: period too long")
)
var Serial = NullSerial{}
Serial is a null device: writes to it are ignored.
var (
ErrTxInvalidSliceSize = errors.New("SPI write and read slices must be same size")
errSPIInvalidMachineConfig = errors.New("SPI port was not configured properly by the machine")
)
func CPUFrequency
func CPUFrequency() uint32
Return the current CPU frequency in hertz.
func InitADC
func InitADC()
InitADC initializes the registers needed for ADC.
func InitSerial
func InitSerial()
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 a ADCPin to be able to be used to read data.
func (ADC) Get
func (a ADC) Get() uint16
Get returns the current value of a ADC pin, in the range 0..0xffff. The AVR has an ADC of 10 bits precision so the lower 6 bits will be zero.
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 PWM
type PWM struct {
num uint8
}
PWM is one PWM peripheral, which consists of a counter and two output channels (that can be connected to two fixed 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.
For Timer0, there is only a limited number of periods available, namely the CPU frequency divided by 256 and again divided by 1, 8, 64, 256, or 1024. For a MCU running at 8MHz, this would be a period of 32µs, 256µs, 2048µs, 8192µs, or 32768µs.
For Timer1, the period is more flexible as it uses OCR1C as the top value. Timer1 also supports more prescaler values (1 to 16384).
func (PWM) Counter
func (pwm PWM) Counter() uint32
Counter returns the current counter value of the timer in this PWM peripheral. It may be useful for debugging.
func (PWM) Period
func (pwm PWM) Period() uint64
Period returns the used PWM period in nanoseconds. It might deviate slightly from the configured period due to rounding.
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, in other words the fraction of time the channel output is high (or low when inverted). For example, to set it to a 25% duty cycle, use:
pwm.Set(channel, pwm.Top() / 4)
pwm.Set(channel, 0) will set the output to low and pwm.Set(channel, pwm.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 Set (see Set documentation 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 sets the pin to input or output.
func (Pin) Get
func (p Pin) Get() bool
Get returns the current value of a GPIO pin when the pin is 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() (*volatile.Register8, uint8)
Return the register and mask to disable a given port. This can be used to implement bit-banged drivers.
Warning: there are no separate pin set/clear registers on the AVR. The returned mask is only valid as long as no other pin in the same port has been changed.
func (Pin) PortMaskSet
func (p Pin) PortMaskSet() (*volatile.Register8, uint8)
Return the register and mask to enable a given GPIO pin. This can be used to implement bit-banged drivers.
Warning: there are no separate pin set/clear registers on the AVR. The returned mask is only valid as long as no other pin in the same port has been changed.
func (Pin) Set
func (p Pin) Set(value bool)
Set changes the value of the GPIO pin. The pin must be configured as output.
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 {
// Delay cycles for frequency control (0 = max speed)
delayCycles uint16
// USICR value configured for the selected SPI mode
usicrValue uint8
// LSB-first mode (requires software bit reversal)
lsbFirst bool
}
SPI is the USI-based SPI implementation for ATTiny85. The ATTiny85 doesn’t have dedicated SPI hardware, but uses the USI (Universal Serial Interface) in three-wire mode.
Fixed pin mapping (directly controlled by USI hardware):
- PB2: SCK (clock)
- PB1: DO/MOSI (data out)
- PB0: DI/MISO (data in)
Note: CS pin must be managed by the user.
func (*SPI) Configure
func (s *SPI) Configure(config SPIConfig) error
Configure sets up the USI for SPI communication. Note: The user must configure and control the CS pin separately.
func (*SPI) Transfer
func (s *SPI) Transfer(b byte) (byte, error)
Transfer performs a single byte SPI transfer (send and receive simultaneously) This implements the USI-based SPI transfer using the “clock strobing” technique
func (*SPI) Tx
func (spi *SPI) Tx(w, r []byte) error
Tx handles read/write operation for SPI interface. Since SPI is a synchronous write/read interface, there must always be the same number of bytes written as bytes read. The Tx method knows about this, and offers a few different ways of calling it.
This form sends the bytes in tx buffer, putting the resulting bytes read into the rx buffer. Note that the tx and rx buffers must be the same size:
spi.Tx(tx, rx)
This form sends the tx buffer, ignoring the result. Useful for sending “commands” that return zeros until all the bytes in the command packet have been received:
spi.Tx(tx, nil)
This form sends zeros, putting the result into the rx buffer. Good for reading a “result packet”:
spi.Tx(nil, rx)
type SPIConfig
type SPIConfig struct {
Frequency uint32
LSBFirst bool
Mode uint8
}
SPIConfig is used to store config info for SPI.
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.