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GPIO.md

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GPIO {#gpio}

Greenwich devices have up to five user-programmable GPIO pins, depending on the model, but at least three inputs and two outputs (open collectors) are available on the entry-level "Java" version:

This is the 14pin Molex connector seen from the back (i.e. plugged into S1 on the Greenwich)

Molex connector

  • GPIO1, Pin S1-5, light-blue cable, topic name: /gpio/1
  • GPIO3, Pin S1-12, grey cable, topic name: /gpio/3
  • GPIO7, Pin S1-11, green ignition cable (normally connected to fuse), topic name: /gpio/7

Inputs

Each input (GPIO 1, 3, 7) has an allowed voltage range of +- VIN (9-32V) with LOW being recognized at <0.5V and HIGH at >3.0V.

The OwnTracks-Edition of the software surfaces the state (HIGH/LOW) of these pins into MQTT publishes by publishing a payload of 1 or 0, respectively, depending on the pin's state. One publish occurs per pin as soon as its state changes.

The topic used for publishing is the general topic of the device with /gpio/<pin> appended to it:

owntracks/acme/van17/gpio/1 0
owntracks/acme/van17/gpio/3 0
owntracks/acme/van17/gpio/7 1

Arduino

In order to toggle these pins with, say, an Arduino, you can use a small sketch on a basic Arduino board. The following is a variation of the blink sketch which flips PIN 10 connected to GPIO1 on the Greenwich every 5 seconds, and blinks LED13 on the Arduino accordingly.

#define LED        13
#define GREENWICH  10

void setup() {
    pinMode(LED, OUTPUT);
    pinMode(GREENWICH, OUTPUT);
}

void loop() {
    digitalWrite(LED, HIGH);
    digitalWrite(GREENWICH, HIGH);
    delay(5000);
    digitalWrite(LED, LOW);
    digitalWrite(GREENWICH, LOW);
    delay(5000);
}

Outputs

The two outputs (open collectors) may draw a maximum current of 300mA (anything above that may destroy your equipment!).

  • GPIO10, Pin S1-13, brown (shown with white border), open collector, mapped onto command out 1
  • GPIO9, Pin S1-6, green (shown with white border), open collector, mapped onto command out 2

To switch a GPIO output, send a command with a payload consisting of the verb (out) followed by a space and the GPIO output number (1 or 2), followed by the desired state (0 or 1). 1 means collector open, so load is switched on.

mosquitto_pub -t owntracks/acme/van17/cmd -m "out 1 0"

This would open pin S1-13 (brown).

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