The I²C interface is commonly used for connecting sensors to data-logging devices like the Hawks. I²C Sensors use 3 lines
- Power (typically 3V3, but sometimes 5V)
- SDA (Serial Data Line) - data is transmitted over this line
- SCL (Serial Clock) - Clock signal
I²C is a multi-controller/multi-target interface - meaning multiple sensors can be connected to the same bus (i.e. you can wire in multiple I²C sensors into the same terminals on the Hawk.
Multiple sensors are managed as each sensor can be given a unique address (the Hawk uses 8-bit addresses). The Hawk will specify which sensor it is aiming to read from.
This means if you want to use multiple of a specific sensor, it will work provided you can give them different addresses.
Some sensors are only sold pre-configured with a single specific address meaning only one will be able to be used.
Wiring
The Ag-Tech1 card pin out is given here: Hawk Baseboard + Plug in Cards - Wiring+Pin Out.
Key connections for an I²C sensor are:
| Function | Hawk IO | |
| I²C SDA | 4 | Connect to sensor SDA |
| 3.3V output | 5 | Connect to sensor 3V3 |
| I²C SCL | 6 | Connect to sensor SCL |
Configuration
Configure Task
We must configure a task and set I²C Action 1 and/or I²C Action 2 as one of the task actions.
This means currently we can configure readings from 2 sensors. If you require more readings, speak to our support team.
Above - Do I²C Action 1 and 2 hourly (sample sensor and log) - and upload the readings every 4 hours.
Configure I²C Action
- Sensor Type
- Chose your sensor type from the dropdown
- Specific sensors need to be integrated. Contact our support team to discuss options if you have a sensor not listed you wish to use
- I²C Address
- Typically leave as 0 to use the default address for the sensor integration
- If you have multiple sensors with multiple addresses you would set the sensor address to read from here
- Analogue Offset
- Set the Hawk Analogue Input to log the sensor reading to
- The offset is where the first reading will be stored (some sensors return multiple readings)
- It is important to be aware of sensors which return multiple values to avoid clashes. Generally, it is best to use analogues 10+ to avoid any clashes
- Sensor Parameter 1-3
- Some specific sensors have additional parameters which these fields are used for. For the majority, this can be left blank