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Remote Control

It is possible to remotely control your devices from another computer, enabling you to develop and test your application directly from your development environment.

Command Line Examples

All of the command line examples provided assume that all dependent JARs are also contained within the current directory or on the CLASSPATH.

Implementations

  1. gRPC
  2. Firmata
  3. pigpio
  4. Particle Wi-Fi Connected Microcontrollers

gRPC

diozero provides its own remote protocol implementation that is based on gRPC via the diozero-remote-common, diozero-provider-remote and diozero-remote-server modules.

Simply run the diozero-remote-server application on the target device then connect to it from a diozero application by adding diozero-provider-remote-1.3.1.jar to the classpath and setting diozero.remote.hostname either via the command line or as an environment variable.

The diozero-remote-server application will also make use of diozero providers. For example, you could run it with diozero-provider-pigpio-1.3.1.jar on the classpath and it would use pigpio for the underlying device communication. You could even chain to another diozero-remove-server instance by using diozero-provider-remote-1.3.1.jar.

Firmata

Firmata compatible devices are supported via the diozero-provider-firmata device factory provider. This provider includes a Firmata protocol implementation that can operate via either serial or sockets interfaces. The serial implementation uses the diozero NativeSerialDevice. I recommend using Firmata Builder to construct a Configurable Firmata implementation that matches your device.

The Firmata implementation should work with any Arduino compatible device. It has been tested with the following devices:

  • Arduino Uno (Serial)
  • Pololu A-Star 32U4 (Serial)
  • Raspberry Pi Pico (*required some minor tweaks) (Serial)
  • ESP8266 (Serial, BLE & WiFi)
  • ESP32 (Serial, BLE & WiFi) - requires latest ConfigurableFirmata

The Firmata adapter first looks for the diozero.firmata.serialPort property - if this set (either via command line or environment variable) the serial communication protocol is used. Otherwise, the adapter will look for the diozero.firmata.tcpHostname property and if set use sockets communication. The sockets port defaults to 3030 but can be override via the diozero.firmata.tcpPort property.

Example command line:

java -cp diozero-sampleapps-1.3.1.jar:diozero-provider-firmata-1.3.1.jar com.diozero.sampleapps.LEDTest -DFIRMATA_PORT=COM5 12

* Fixes for Raspberry Pi Pico:

/Applications/Arduino.app/Contents/Java/libraries/Firmata/Boards.h or ~/Documents/Arduino/libraries/ConfigurableFirmata/src/utility/Boards.h:

// Raspberry Pi Pico
// https://datasheets.raspberrypi.org/pico/Pico-R3-A4-Pinout.pdf
#elif defined(TARGET_RP2040) || defined(TARGET_RASPBERRY_PI_PICO)
#define TOTAL_ANALOG_PINS       4
#define TOTAL_PINS              30
#define VERSION_BLINK_PIN       LED_BUILTIN
#define IS_PIN_DIGITAL(p)       (((p) >= 0 && (p) < 23) || (p) == LED_BUILTIN)
#define IS_PIN_ANALOG(p)        ((p) >= 26 && (p) < 26 + TOTAL_ANALOG_PINS)
#define IS_PIN_PWM(p)           digitalPinHasPWM(p)
#define IS_PIN_SERVO(p)         (IS_PIN_DIGITAL(p) && (p) != LED_BUILTIN)
// From the data sheet I2C-0 defaults to GP 4 (SDA) & 5 (SCL) (physical pins 6 & 7)
// However, v2.3.1 of mbed_rp2040 defines WIRE_HOWMANY to 1 and uses the non-default GPs 6 & 7:
//#define WIRE_HOWMANY	(1)
//#define PIN_WIRE_SDA            (6u)
//#define PIN_WIRE_SCL            (7u)
#define IS_PIN_I2C(p)           ((p) == PIN_WIRE_SDA || (p) == PIN_WIRE_SCL)
// SPI-0 defaults to GP 16 (RX / MISO), 17 (CSn), 18 (SCK) & 19 (TX / MOSI) (physical pins 21, 22, 24, 25)
#define IS_PIN_SPI(p)           ((p) == PIN_SPI_SCK || (p) == PIN_SPI_MOSI || (p) == PIN_SPI_MISO || (p) == PIN_SPI_SS)
// UART-0 defaults to GP 0 (TX) & 1 (RX)
#define IS_PIN_SERIAL(p)        ((p) == 0 || (p) == 1 || (p) == 4 || (p) == 5 || (p) == 8 || (p) == 9 || (p) == 12 || (p) == 13 || (p) == 16 || (p) == 17)
#define PIN_TO_DIGITAL(p)       (p)
#define PIN_TO_ANALOG(p)        ((p) - 26)
#define PIN_TO_PWM(p)           (p)
#define PIN_TO_SERVO(p)         (p)

~/Documents/Arduino/libraries/ConfigurableFirmata/src/ConfigurableFirmata.h:

//#define I2C                     0x06 // same as PIN_MODE_I2C

pigpio

The pigpio library also comes with the pigpiod daemon process for remote access. By default (for security reasons) this process only allows communication from the Raspberry Pi device it is running on. To enable remote access pigpiod needs to be run without the -l option. Before doing this you must be aware of the security implications, only consider this on a local network that has no inbound connectivity from the Internet.

On Raspbian Jessie and later you can enable the pigpiod daemon to run as a system service:

sudo systemctl enable pigpiod.service

This will start pigpiod every time the Pi boots. To remove the -l option which is included by default, edit /etc/systemd/system/pigpiod.service.d/public.conf and change the ExecStart property, i.e.

ExecStart=/usr/bin/pigpiod

If the file doesn’t exist, run the raspi-config application and choose “3 Interface Options”, “P8 Remote GPIO” and select “Yes”. This will make the appropriate changes and create that file if it didn’t already exist.

Make sure you set the property PIGPIOD_HOST to the hostname of your Raspberry Pi. You can also override the default pigpiod port value (8888) via the property PIGPIOD_PORT. Again these properties can be set either via command line or as environment variables.

Example command line:

java -cp diozero-sampleapps-1.3.1.jar:diozero-provider-pigpio-1.3.1.jar -DPIGPIOD_HOST=raspberrypi com.diozero.sampleapps.LEDTest 12

Particle Wi-Fi Connected Microcontrollers

The Particle Photon is a tiny Wi-Fi connected microcontroller. You can upload the VoodooSpark firmware to the board to enable remote control over Wi-Fi.

Make sure you set the properties PARTICLE_DEVICE_ID and PARTICLE_TOKEN correctly (either via command line or as environment variables).

Example command line:

java -cp diozero-sampleapps-1.3.1.jar:diozero-provider-voodoospark-1.3.1.jar -DPARTICLE_DEVICE_ID=abc -DPARTICLE_TOKEN=xyz com.diozero.sampleapps.LEDTest 12