Now in FeatherWing form factor, this can still be used as a wired-in module for any AVR based Arduino.

NOTICE 3/25/2021: Apparently not compatible with SAMD21 based Arduinos - output is flaky on these controllers. This is probably fixable in the library as it appears to be related to timing calculations not to do with the hardware. I'm investigating.

What is it?

This module - and the associated library - allow you to connect eight HC-SR04 ultrasonic range sensors to an Arduino using the I2C bus and one hardware interrupt pin. I used to sell a 16 sensor version - the OctoSonarX2.

Why did you make it?

I wanted more sensors on my robot to help it navigate. I'm too cheap to buy a mega board with enough pins or smarter sensors that need less pins.

What makes it special?

The library handles all the timing, and the hardware interrupts provide surprisingly high accuracy. Each unit is individually tested using an Arduino test-bed and ships with separate pin headers.

Hookup Instructions: Feather controller.

If you are using a Feather board, solder on your preferred FeatherWing headers (not included) and plug the OctoSonar into your Feather board as you would any other Wing.

Note the following:

• I2C address is set to 0x38. This can be changed via solder jumpers on the back.
• 4.7k I2C pullup resistors are on the board. They may be disconnected by cutting solder jumpers on the back.
• the product uses one hardware interrupt pin in addition to I2C. This is connected to the third GPIO pin (count from BAT) which corresponds to Arduino pin 2 on the Feather 328P. This is highlighted in white. Other boards may need a different pin. This can be changed by cutting and soldering jumpers on the back.
• HC-SR04 sensors require a 5V supply, while the the Feather standard is 3.3V. There are now HC-SR04-P sensors which can run on 3.3V or 5V, apparently with shorter range for 3.3V. On the Octosonar the sensor voltage is called VS. By default this is connected to the USB power pin. If your Feather is not running off a 5V supply, this will be dead. To run the whole system on 3.3V (e.g. battery) you need to cut jumper V2 to disconnect VS from USB, and connect jumper V1 which connect VS to 3.3V/VCC, and use HC-SR04-P sensors.
• the OctoSonar includes a reset button for Feather users.

Hookup Instructions: wired connections.

The OctoSonar is an I2C bus device and you will connect it to the I2C bus on your controller. Please refer to your controller documentation for which pin is which on your controller. In addition you will need to connect one hardware interrupt pin and possibly an additional power connection.

• connect the SDA, SCL, VCC and GND pins as you would for any I2C device. If your controller is a 3.3V device, VCC will be 3.3V - if it is a 5V device it will be 5V.
• 4.7k I2C pullups are included on the board. These may be disconnected by cutting solder jumpers on the back.
• I2C address is 0x38 and can be changed via solder jumpers
• The board takes power from VCC, but the sensors take a separate power feed from the VS pin. This allows us to use 5V HC-SR04 sensors with a 3.3V controller. HC-SR04-P sensors can operate at 3.3V or 5V with more range at 5V. If your desired VS voltage is the same as VCC, you can avoid the extra wire and join VS to VCC with the V1 jumper. If you connect V1, always cut V2 - this will protect Feather boards if you use them with the OctoSonar in future.
• connect a hardware interrupt pin to the INT pin. See your controller documentation for appropriate pins to use. Pin 2 on the Arduino Uno works.
• the reset button on the board is only functional when the board is installed as a FeatherWing

Hookup Instructions: sensors.

Each sensor connects with 4 wires marked V, T, E and G for Voltage, Trigger, Echo and Ground. Sensors can be connected individually using 4-pin cables connected to the vertical columns of 4 pins numbered 0 thru 7 at the right of the board.

If you are mounting the sensors on my Trimount brackets, each Trimount can support 3 sensors with only two cables by sharing the V and G connections. To do this solder two 4 pin headers horizontally in the locations marked out in white. Wire two 4-pin cables to the matching locations on the Trimount bracket. This leaves one sensor location free in in the header block - you can connect another sensor there as before.

Note that the code library that I support is only for the Arduino environment. While electronically compatible with Raspberry Pi, this product is not supported in software yet. Feel free to help at https://github.com/arielnh56/SonarI2C-RPi. The code at this location is primarily a customer contribution - I am unable to provide support.

Use the OctoSonar library, not the SonarI2C library

I am stocking some of the sensors and cables too, so you can get them at the same time. These are batch tested to verify that they are not the type with the echo-lock problem. See this thread on the Arduino forum

Please check out the Hackaday documentation and the github library for more info.

Base package includes the module and 40 header pins

Robot pack includes:

• the module and headers
• 8 sensors
• 8 cables
• 4 trimount brackets with standoffs
• 40 more header pins for the brackets
• save on shipping - counts as only one item for shipping calculation

Note that the picture pre-dates the creation of the trimount brackets. They look a lot better than the bent aluminum and sticky pads shown.

The video below describes the operation of the board. It shows the earlier 2.1 version board which has all the same components just arranged differently, and does not have the FeatherWing reset pin.