uBit.io#

Overview#

uBit.io provides a means of accessing the pins exposed on the edge connector, enabling Analog and Digital Input/Output operations. Some pins can also perform basic touch sensing through resistance detection.

There are 6 Analog capable pins which can be used to generate Analog wave forms and approximate Analog inputs. There is only one Analog to Digital converter on the NRF51822, which prevents concurrent analog to digital conversions.

Analog waveforms are simulated via Pulse Width Modulation generated by software. As such, there is a limit of 3 concurrent PWM outputs.

There are two ways of accessing pins on the edge connector:

  • uBit.io.P0.setDigitalValue(1) - Would configure P0 as a digital output, and set that pin HI.
  • uBit.io.pin[1].setDigitalValue(1) - Would configure P1 as a digital output, and set that pin HI.

By design, the operation of the pins on the edge connector are dynamic, and can swap between modes based on the method that as been called.

For example:

while(1)
{
    uBit.io.P0.setDigitalValue(1);
    uBit.sleep(1000);
    uBit.io.P0.setServoValue(90);
    uBit.sleep(1000);
}

Will transition between Digital and Analog output every second.

Shared Functionality#

As well as being General Purpose Input Output (GPIO) pins, some pins on the micro:bit have other functionality used internally by the micro:bit.

Therefore, some functionality on the micro:bit may have to be disabled in order to use some GPIO pins.

This is illustrated by the diagram below:

microbit schematic

Message Bus ID#

Constant Value Capability
MICROBIT_ID_IO_P0 7 Analog, digital and touch
MICROBIT_ID_IO_P1 8 Analog, digital and touch
MICROBIT_ID_IO_P2 9 Analog, digital and touch
MICROBIT_ID_IO_P3 10 Analog and digital
MICROBIT_ID_IO_P4 11 Analog and digital
MICROBIT_ID_IO_P5 12 Digital only
MICROBIT_ID_IO_P6 13 Digital only
MICROBIT_ID_IO_P7 14 Digital only
MICROBIT_ID_IO_P8 15 Digital only
MICROBIT_ID_IO_P9 16 Digital only
MICROBIT_ID_IO_P10 17 Analog and digital
MICROBIT_ID_IO_P11 18 Digital only
MICROBIT_ID_IO_P12 19 Digital only
MICROBIT_ID_IO_P13 20 Digital only
MICROBIT_ID_IO_P14 21 Digital only
MICROBIT_ID_IO_P15 22 Digital only
MICROBIT_ID_IO_P16 23 Digital only
MICROBIT_ID_IO_P19 24 Digital only
MICROBIT_ID_IO_P20 25 Digital only

Message Bus Events#

When isTouched() is called, provided that the selected pin has touch capabilities (outlined above), an instance of button will be created. Listeners can therefore be placed using the desired pins’ ID, with the exact same events produced by a standard button.

uBit.messageBus.listen(MICROBIT_ID_IO_P0, MICROBIT_EVT_ANY, someFunction);
uBit.io.P0.isTouched();
Constant Value
MICROBIT_BUTTON_EVT_DOWN 1
MICROBIT_BUTTON_EVT_UP 2
MICROBIT_BUTTON_EVT_CLICK 3
MICROBIT_BUTTON_EVT_LONG_CLICK 4
MICROBIT_BUTTON_EVT_HOLD 5
MICROBIT_BUTTON_EVT_DOUBLE_CLICK 6

API#

Constructor#


MicroBitPin(
int
id,
PinName
name,
PinCapability
capability)#

Description#

Constructor. Create a MicroBitPin instance, generally used to represent a pin on the edge connector.

Parameters#

int
id - the unique EventModel id of this component.

PinName
name - the mbed PinName for this MicroBitPin instance.

PinCapability
capability - the capabilities this MicroBitPin instance should have. (PIN_CAPABILITY_DIGITAL, PIN_CAPABILITY_ANALOG, PIN_CAPABILITY_AD, PIN_CAPABILITY_ALL)

Example#
 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_ALL);

setDigitalValue#


int
setDigitalValue
(
int
value)#

Description#

Configures this IO pin as a digital output (if necessary) and sets the pin to ‘value’.

Parameters#

int
value - 0 (LO) or 1 (HI)

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have digital capability.

Example#
 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_BOTH); 
 P0.setDigitalValue(1); // P0 is now HI

getDigitalValue#


int
getDigitalValue
()#

Description#

Configures this IO pin as a digital input (if necessary) and tests its current value.

Returns#

1 if this input is high, 0 if input is LO, or MICROBIT_NOT_SUPPORTED if the given pin does not have digital capability.

Example#
 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_BOTH); 
 P0.getDigitalValue(); // P0 is either 0 or 1;


int
getDigitalValue
(
PinMode
pull)#

Description#

Configures this IO pin as a digital input with the specified internal pull-up/pull-down configuraiton (if necessary) and tests its current value.

Parameters#

PinMode
pull - one of the mbed pull configurations: PullUp, PullDown, PullNone

Returns#

1 if this input is high, 0 if input is LO, or MICROBIT_NOT_SUPPORTED if the given pin does not have digital capability.

Example#
 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_BOTH); 
 P0.getDigitalValue(PullUp); // P0 is either 0 or 1;

setAnalogValue#


int
setAnalogValue
(
int
value)#

Description#

Configures this IO pin as an analog/pwm output, and change the output value to the given level.

Parameters#

int
value - the level to set on the output pin, in the range 0 - 1024

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

setServoValue#


int
setServoValue
(
int
value)#

Description#

Configures this IO pin as an analog/pwm output (if necessary) and configures the period to be 20ms, with a duty cycle between 500 us and 2500 us.

A value of 180 sets the duty cycle to be 2500us, and a value of 0 sets the duty cycle to be 500us by default.

This range can be modified to fine tune, and also tolerate different servos.

Parameters#

int
value - the level to set on the output pin, in the range 0 - 180.

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

int
setServoValue
(
int
value,
int
range)#

Description#

Configures this IO pin as an analog/pwm output (if necessary) and configures the period to be 20ms, with a duty cycle between 500 us and 2500 us.

A value of 180 sets the duty cycle to be 2500us, and a value of 0 sets the duty cycle to be 500us by default.

This range can be modified to fine tune, and also tolerate different servos.

Parameters#

int
value - the level to set on the output pin, in the range 0 - 180.

int
range - which gives the span of possible values the i.e. the lower and upper bounds (center +/- range/2). Defaults to MICROBIT_PIN_DEFAULT_SERVO_RANGE.

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

int
setServoValue
(
int
value,
int
range,
int
center)#

Description#

Configures this IO pin as an analog/pwm output (if necessary) and configures the period to be 20ms, with a duty cycle between 500 us and 2500 us.

A value of 180 sets the duty cycle to be 2500us, and a value of 0 sets the duty cycle to be 500us by default.

This range can be modified to fine tune, and also tolerate different servos.

Parameters#

int
value - the level to set on the output pin, in the range 0 - 180.

int
range - which gives the span of possible values the i.e. the lower and upper bounds (center +/- range/2). Defaults to MICROBIT_PIN_DEFAULT_SERVO_RANGE.

int
center - the center point from which to calculate the lower and upper bounds. Defaults to MICROBIT_PIN_DEFAULT_SERVO_CENTER

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

getAnalogValue#


int
getAnalogValue
()#

Description#

Configures this IO pin as an analogue input (if necessary), and samples the Pin for its analog value.

Returns#

the current analogue level on the pin, in the range 0 - 1024, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

Example#
 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_BOTH); 
 P0.getAnalogValue(); // P0 is a value in the range of 0 - 1024

isInput#


int
isInput
()#

Description#

Determines if this IO pin is currently configured as an input.

Returns#

1 if pin is an analog or digital input, 0 otherwise.

isOutput#


int
isOutput
()#

Description#

Determines if this IO pin is currently configured as an output.

Returns#

1 if pin is an analog or digital output, 0 otherwise.

isDigital#


int
isDigital
()#

Description#

Determines if this IO pin is currently configured for digital use.

Returns#

1 if pin is digital, 0 otherwise.

isAnalog#


int
isAnalog
()#

Description#

Determines if this IO pin is currently configured for analog use.

Returns#

1 if pin is analog, 0 otherwise.

isTouched#


int
isTouched
()#

Description#

Configures this IO pin as a “makey makey” style touch sensor (if necessary) and tests its current debounced state.

Users can also subscribe to MicroBitButton events generated from this pin.

Returns#

1 if pin is touched, 0 if not, or MICROBIT_NOT_SUPPORTED if this pin does not support touch capability.

Example#
 MicroBitMessageBus bus; 

 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_ALL); 
 if(P0.isTouched()) 
 { 
 //do something! 
 } 

 // subscribe to events generated by this pin! 
 bus.listen(MICROBIT_ID_IO_P0, MICROBIT_BUTTON_EVT_CLICK, someFunction);

setServoPulseUs#


int
setServoPulseUs
(
int
pulseWidth)#

Description#

Configures this IO pin as an analog/pwm output if it isn’t already, configures the period to be 20ms, and sets the pulse width, based on the value it is given.

Parameters#

int
pulseWidth - the desired pulse width in microseconds.

Returns#

MICROBIT_OK on success, MICROBIT_INVALID_PARAMETER if value is out of range, or MICROBIT_NOT_SUPPORTED if the given pin does not have analog capability.

setAnalogPeriod#


int
setAnalogPeriod
(
int
period)#

Description#

Configures the PWM period of the analog output to the given value.

Parameters#

int
period - The new period for the analog output in milliseconds.

Returns#

MICROBIT_OK on success, or MICROBIT_NOT_SUPPORTED if the given pin is not configured as an analog output.

setAnalogPeriodUs#


int
setAnalogPeriodUs
(
int
period)#

Description#

Configures the PWM period of the analog output to the given value.

Parameters#

int
period - The new period for the analog output in microseconds.

Returns#

MICROBIT_OK on success, or MICROBIT_NOT_SUPPORTED if the given pin is not configured as an analog output.

getAnalogPeriodUs#


int
getAnalogPeriodUs
()#

Description#

Obtains the PWM period of the analog output in microseconds.

Returns#

the period on success, or MICROBIT_NOT_SUPPORTED if the given pin is not configured as an analog output.

getAnalogPeriod#


int
getAnalogPeriod
()#

Description#

Obtains the PWM period of the analog output in milliseconds.

Returns#

the period on success, or MICROBIT_NOT_SUPPORTED if the given pin is not configured as an analog output.

setPull#


int
setPull
(
PinMode
pull)#

Description#

Configures the pull of this pin.

Parameters#

PinMode
pull - one of the mbed pull configurations: PullUp, PullDown, PullNone

Returns#

MICROBIT_NOT_SUPPORTED if the current pin configuration is anything other than a digital input, otherwise MICROBIT_OK.

eventOn#


int
eventOn
(
int
eventType)#

Description#

Configures the events generated by this MicroBitPin instance.

MICROBIT_PIN_EVENT_ON_EDGE - Configures this pin to a digital input, and generates events whenever a rise/fall is detected on this pin. (MICROBIT_PIN_EVT_RISE, MICROBIT_PIN_EVT_FALL) MICROBIT_PIN_EVENT_ON_PULSE - Configures this pin to a digital input, and generates events where the timestamp is the duration that this pin was either HI or LO. (MICROBIT_PIN_EVT_PULSE_HI, MICROBIT_PIN_EVT_PULSE_LO) MICROBIT_PIN_EVENT_ON_TOUCH - Configures this pin as a makey makey style touch sensor, in the form of a MicroBitButton . Normal button events will be generated using the ID of this pin. MICROBIT_PIN_EVENT_NONE - Disables events for this pin.

Parameters#

int
eventType - One of: MICROBIT_PIN_EVENT_ON_EDGE, MICROBIT_PIN_EVENT_ON_PULSE, MICROBIT_PIN_EVENT_ON_TOUCH, MICROBIT_PIN_EVENT_NONE

Returns#

MICROBIT_OK on success, or MICROBIT_INVALID_PARAMETER if the given eventype does not match

Example#
 MicroBitMessageBus bus; 

 MicroBitPin P0(MICROBIT_ID_IO_P0, MICROBIT_PIN_P0, PIN_CAPABILITY_BOTH); 
 P0.eventOn(MICROBIT_PIN_EVENT_ON_PULSE); 

 void onPulse(MicroBitEvent evt) 
 { 
 int duration = evt.timestamp; 
 } 

 bus.listen(MICROBIT_ID_IO_P0, MICROBIT_PIN_EVT_PULSE_HI, onPulse, MESSAGE_BUS_LISTENER_IMMEDIATE)

Note

In the MICROBIT_PIN_EVENT_ON_PULSE mode, the smallest pulse that was reliably detected was 85us, around 5khz. If more precision is required, please use the InterruptIn class supplied by ARM mbed.