Documentation for Tessel's hardware APIs. These are available for code running on Tessel, and is imported by require('tessel').
Tessel is the root object for each of the different ports on the device.
var tessel = require('tessel'); // import tessel
var gpio = tessel.port['GPIO']; // select the GPIO port
gpio.digital[1].write(1); // turn digital pin #1 high # map<Port> tessel.port = {}
A list of ports available on Tessel. Keys for this are "A", "B", "C", "D", or "GPIO".
# array<Pin> tessel.led = []
An array of 4 LEDs available on the Tessel board. These are Pin objects. Their board order is different than their array index order; they're in rainbow order on the board. See below:
| Index | Position (from micro-USB) | Color | Name |
|---|---|---|---|
| 0 | 3rd | Green | LED1 |
| 1 | 4th | Blue | LED2 |
| 2 | 1st | Red | Error |
| 3 | 2nd | Amber | Conn |
// Toggle an LED every 200ms
(function blink (value) {
tessel.led[1].write(value);
setTimeout(blink, 200, !value);
})(true)GPIO access for digital and analog signal lines. Each port exposes its available pins through the .pin, .digital, .analog, and .pwm arrays.
var tessel = require('tessel'); // import tessel
var gpio = tessel.port['GPIO']; // select the GPIO port
gpio.digital.map(function (pin, i) {
console.log('Value of digital pin', i, '=', pin.read());
})
gpio.analog.map(function (pin, i) {
console.log('Value of analog pin', i, '=', pin.read() * pin.resolution, '/', pin.resolution);
})Ports A, B, C, and D have 3 digital pins which can be addressed as such:
tessel.port['A'].digital[0];
tessel.port['A'].digital[1];
tessel.port['A'].digital[2];Additionally the pins can be addressed by the silkscreen printed on Tessel:
tessel.port['A'].pin['G1']; // this is the same as digital[0]
tessel.port['A'].pin['G2']; // this is the same as digital[1]
tessel.port['A'].pin['G3']; // this is the same as digital[2] # string port.id
The unique ID of this port. On Tessel, this would be one of "A", "B", "C", "D", or "GPIO".
# array<number> port.digital = []
An array of which pins are digital inputs/outputs. Has 3 pins for ports A, B, C, and D and 6 pins for the GPIO port.
# array<number> port.analog = []
An array of which pins are analog inputs. Is only available on the GPIO port.
# array<number> port.pwm = []
An array of which pins are PWM outputs (may overlap analog array).
# port.pwmFrequency ( frequency )
Sets the frequency of PWM for a given port. Only the GPIO bank supports PWM pins on Tessel.
# array<number> port.pin = []
An array of all pins on the port. You can differentiate them by their .type and .isPWM attributes.
# new port.Pin ( pin )
Create and return pin object.
# string pin.type
"digital" or "analog".
# number pin.resolution
Digital pins: 1. Analog pins: ADC resolution of output pins ( e.g. 1023 for Tessel ).
# pin.input()
Set pin to be an input.
# pin.output ( value )
Set pin to be an output with value value. Note that the Analog pins cannot be outputs.
# pin.rawDirection( isOutput )
Set pin as input or output.
# pin.write ( value )
Behaves the same as pin.output. Sets pin as an output with value. Digital pins: output is set HIGH if value is truthy, otherwise LOW.
# pin.pwmDutyCycle ( dutyCycleFloat )
Creates a PWM signal with a duty cycle of dutyCycleFloat, the fraction of the PWM period in which the signal is high. Range is between [0-1] inclusive. Only works with pins with true property of isPWM.
# pin.rawWrite ( value )
Sets the pin to value. Does not change the direction of the pin.
# pin.read ()
Sets the pin as an input and reads a digital or analog value. For digital pins, 1 is returned if the value is HIGH, otherwise 0 if LOW. For analog pins the range is between [1-0] inclusive.
# pin.rawRead ()
Reads from the pin *without first setting the direction as an input. Only available on digital pins.
# pin.pull ( mode )
Sets the pin as a pullup, pulldown, or neutral pin. Mode is one of pullup, pulldown or none. Passing in no argument is equivalent to none.
# pin.mode ()
Returns the mode of the pin.
External GPIO Interrupts can be used much like regular Node EventEmitters. There are seven external interrupts you can work with. You can read more in depth discussion about gpio interrupts in our External GPIO Walkthrough.
# pin.on ( type, callback(time, type) )
Sets a listener for a signal edge on pin. time is the milliseconds since boot up and type can be one of rise, fall, change. The high and low level triggers cannot be used with on because they would fire repeatedly and wreak havoc on the runtime.
# pin.once ( type, callback(time, type) )
Sets a listener for a a single event of the trigger type on the pin. time is the milliseconds since boot up and type can be one of rise, fall, change, high, or fall.
# pin.removeListener ( type, listener )
Removes the listener callback for a given type of trigger (eg. 'rise' or 'high') on a pin.
# pin.removeAllListeners ( type )
Removes all of the listeners for a given trigger type on a pin.
Tessel has two buttons. The reset button (nearer to the edge of the board) will stop running any program that is currently executing and restart the microcontroller (erasing any memory in RAM).
The config button will eventually be used for other purposes but is currently a simple way to get user feedback into a script:
var tessel = require('tessel');
tessel.button.on('press', function(time) {
console.log('the button was pressed!', time);
});
tessel.button.on('release', function(time) {
console.log('button was released', time);
});Please note that the button press and release events will use one of the seven External GPIO Interrupts (for one or both events).
The buttons can also be used to put the board into DFU Mode which can be understood as the stage just prior to reprogramming the board. This is useful if the board is no longer able to communicate like typical with a host computer. To activate DFU mode, hold down the config button while pressing and releasing the reset button so that the config button is pressed down when the board comes out of a reset. Then release the config button.
A SPI channel.
var port = tessel.port['A'];
var spi = new port.SPI({
clockSpeed: 4*1000*1000, // 4MHz
cpol: 1, // polarity
cpha: 0, // clock phase
});
spi.transfer(new Buffer([0xde, 0xad, 0xbe, 0xef]), function (err, rx) {
console.log('buffer returned by SPI slave:', rx);
}) # new port.SPI ( [options] )
Creates a SPI object. Options is an object specifying any of the following:
- channel (optional) — An optional numeric index for selecting a SPI channel. Defaults to the first (or only) SPI channel.
- clockSpeed (default
100000) — SPI clock speed in Hz. - cpol (default
0) — Clock polarity. Options are 0 or 1, or 'low' and 'high'. - cpha (default
0) — Clock phase. Options are 0 or 1, or 'first' and 'second'. - dataMode (default
0) — An alternative to defining cpol and cpha explicitly, you can use mode numbers. - bitOrder (default
"msb") — Bit order, most significant bit first or least. Options are 'msb' or 'lsb'. - frameMode (default
"normal") — SPI frame format. Only one format is supported at the moment,"normal". - chipSelect (default
null) — Pin to use as a default chip select pin. If a pin is specified, this pin is toggled in master mode whenever data is to be sent/received on the bus. - chipSelectActive (default
"low") — If a chipSelect pin is specified, this defines the polarity of the CS line when active. - role (default
master) — Determines the role the SPI channel plays, either "master" or "slave". (Currently not supported.)
# spi.transfer ( txbuf, callback(err, rxbuf) )
Transfers a Buffer txbuf to the slave and receives a response in rxbuf.
# spi.receive ( len, callback(err, rxbuf) )
Reads len bytes from a slave. Returns a buffer.
# spi.send ( txbuf, callback(err) )
Sends a Buffer txbuf to the slave.
# spi.setClockSpeed ( clockspeed ) Sets the clockspeed.
# spi.setDataMode ( mode ) Sets the data mode.
# spi.setFrameMode ( mode ) Sets the frame mode.
# spi.setRole ( role ) Sets the role.
# spi.setChipSelectMode ( mode ) Sets the chip select settings.
# spi.lock ( callback ) Locks SPI so that only one SPI port is communicating at a time. To read more about SPI Bus Locking, check out our discussion about the Bus Locking and Raw Transfers API.
An I2C channel.
var port = tessel.port['A'];
var slaveAddress = 0xDE;
var i2c = new port.I2C(slaveAddress)
i2c.transfer(new Buffer([0xde, 0xad, 0xbe, 0xef]), function (err, rx) {
console.log('buffer returned by I2C slave ('+slaveAddress.toString(16)+'):', rx);
}) # new port.I2C ( address, [idx] )
Creates an I2C channel for a device of a specific address. Multiple I2C channels can be used in parallel.
# i2c.transfer ( txbuf, rxbuf_len, callback(err, rxbuf) )
Transfers a Buffer txbuf to the client and receives a response of length rxbuf_len.
# i2c.receive ( rxbuf_len, callback(err, rxbuf) )
Reads rxbuf_len bytes from a client.
# i2c.send ( txbuf, callback(err) )
Sends a Buffer txbuf to the client.
A UART channel.
var port = tessel.port['A'];
var uart = new port.UART({
baudrate: 115200
})
uart.write('ahoy hoy\n')
uart.on('data', function (data) {
console.log('received:', data);
})
// UART objects are streams!
// pipe all incoming data to stdout:
uart.pipe(process.stdout);
}) # new port.UART ( [idx[, options]] ) implements DuplexStream
Creates a UART channel. Defaults: {"baudrate": 9600, "dataBits": 8, "parity": "even", "stopBits": 2}
# array<number> uart.baudRates = []
An array of valid baud rates supported by the system.
# uart.setBaudRate ( rate )
Sets the baud rate to a valid rate in baudRates.
# uart.setDataBits ( bits )
Sets the number of data bits to the number 5, 6, 7, or 8.
# uart.setStopBits ( bits )
Sets the number of data bits to the number 1 or 2.
# uart.setParity ( parity )
Sets the parity to the value "none", "odd", or "even".
# uart.write ( buf )
Writes a buffer to the UART connection.
# uart → emits "data"
Data that arrives over the UART channel is sent as a Node.js stream.
# process.sendfile ( filename, buffer ) A buffer can be sent over USB to a file named filename on a host computer's file system. You must start the script with -u and the argument of which directory to save the folder. For example, tessel run test.js -u ./recordings will save the file in the recordings directory.
# tessel.deviceId ( ) Get the Inique ID of your Tessel.
MIT