Google's Coral-Enviromental-Sensor-Board in Raspberry Pi Zero Hat format compatible with RPi3 Rpi4 Rpi Zero W
- 128x32 OLED display
- Ambient light sensor (OPT3002)
- Barometric pressure sensor (BMP280)
- Humidity / temperature sensor (HDC2010)
- Cryptoprocessor (ATECC608A) with Google keys
- 40-pin GPIO female connector
- Four Grove connectors:
- 1x UART
- 1x I2C
- 1x PWM
- 1x 3.3/5V analog
- General purpose button
- General purpose LED
The Environmental Sensor Board is an add-on board (also known as a pHAT or bonnet) that adds sensing capabilities to your Coral Dev Board or Raspberry Pi projects. (It includes an EEPROM for compatibility with Raspberry Pi boards.)
The board provides atmospheric data such as light level, barometric pressure, temperature, and humidity. You can also attach additional sensors with the Grove connectors.
The board also includes a secure cryptoprocessor with Google keys to enable connectivity with Google Cloud IoT Core services, allowing you to securely connect to the device and then collect, process, and analyze the sensor data.
| Measurement | Value |
|---|---|
| Board size | Board w/ components: 65 x 30 x 18.46 mm 40-pin header height: 8.5 mm |
| Hole size/spacing | Diameter: 2.4 mm Horizontal spacing: 58 mm Vertical spacing: 23 mm |
| Weight | 14 g |
The board must be connected to a host with I2C, SPI, and 3.3V power. The 40-pin GPIO header and provided software are designed to work with the Coral Dev Board or Raspberry Pi (running Mendel Linux or Raspbian, respectively).
All sensors are connected to the I2C lines from header pins 3 and 5 (see the header pinout).
| Sensor | Details |
|---|---|
| Humidity and temperature sensor | Texas Instruments HDC2010:
I2C address: 0x40 |
| Ambient light sensor | Texas Instruments OPT3002:
I2C address: 0x45 |
| Barometric pressure sensor | Bosch Sensortec BMP280:
I2C address: 0x76 |
The Grove connectors provide easy access to the PWM, UART, and I2C pins from the baseboard, plus an on-board analog-to-digital converter (ADC), as illustrated in figure 2.
To interact with the AIN0 analog source, use address 0x49 on the I2C lines from header pins 3 and 5 (see the header pinout).
The 128x32 OLED display is driven by the SSD1306 control chip, connected with the SPI interface.
| SPI function | Pin |
|---|---|
| MOSI | 19 |
| MISO | 21 |
| SCLK | 23 |
| CL | 24 |
| RESET | 22 |
| DC | 18 |
The board includes a secure cryptoprocessor (ATECC608A) with an EEPROM that can store up to 16 keys (256-bit), certificates, or other data. Although this chip provides a range of cryptographic features, it is primarily included to provide secure key generation and management so you can securely authenticate with the device when deployed into the field.
The factory setting for the Environmental Sensor Board includes one Google key (private key, public key, and certificate) to enable communication with Google Cloud IoT Core right out of the box. This key slot is reusable, just like the rest of the memory, so you don't have to keep it.
Figure 3 shows which pins from the baseboard are used by the Environmental Sensor Board. Pins highlighted in dark green are used by the board and not available to you (except through software for the corresponding functions), while the pins in light green are used by the board but are still available to you through the Grove connectors.
| Device | Address |
|---|---|
| Humidity/temp sensor | 0x40 |
| Ambient light sensor | 0x45 |
| Barometric pressure sensor | 0x76 |
| Analog Grove connector | 0x49 |
| Cryptoprocessor | 0x30 |
This is the Linux kernel IIO drivers for the sensors used in the Coral Environment Sensor board.
Note: These files are mostly identical to the drivers in mainline linux (iio/). There are trivial changes for ease of use for DKMS.