What About Bluetooth?
Bluetooth protocol has been a leader in point-to-point communication since the 2nd generation came out in 2005 and the market exploded with music streaming devices.
Newer versions of Bluetooth have extremely low power, increased security, and increased range. Bluetooth 4.2 and 5.0 are generally used in smart devices (such as smart watches) to send small amounts of data such as temperature or heart rate readings. Bluetooth 5.0 increased range by up to 4x over previous versions.
Breadware’s challenge was to see if the new Bluetooth 5.0 had extended range enough to be used as a robot remote control. The robot needed to respond quickly (reaction time of < 50ms), have basic security protocols to prevent anyone from hacking in and causing damage, have a long battery life, be able to download logs to a cell phone and be FCC certified.
Our Approach, Findings, & Solution
Breadware experimented with various Bluetooth integrated circuits and landed on the Ublox NINA-B3 module. This module contains Nordic’s NRF52840 System on Chip and not only has FCC certification with a variety of antennas, but also IC (Canada), ETSI (Europe), MIC (Japan), and others.
Nordic’s NRF52840 is one of the most widely used modern Bluetooth low energy microcontrollers. At the core is an Arm-Cortex processor which is easy to learn to program. Nordic has a robust software development kit (SDK) with a large variety of firmware examples, including long-range tests. These range test examples let you experiment with a large number of Bluetooth settings to find the optimal connection parameters.
To create a remote control, Breadware tested using the long-range Bluetooth (encoded 4x range), maximum power output (+8dBm), 7.5ms connection interval and no data length extension. This 7.5ms interval allowed multiple packets to be dropped from interference or corruption before the critical 50ms robot response time was lost.
What we found was that the range of these settings was 400+ft in an industrial park. These tests were run with lots of trees, buildings and wifi networks potentially causing interference.
Power consumption of the Bluetooth module was capped to below 11mA in this mode, meaning that the remote control could be run on D batteries for days on end. When the remote control is set on the shelf, the nrf52840 enters an ultra-low power mode, sipping < 0.01mA and extending the shelf life to years.
The Bluetooth module on the remote controller scanned for the robot Bluetooth module, found the required identification code and formed a secure bond. If a hacker tried to connect to the robot without these identification codes, they would be unable to do so without great difficulty.
Log downloading to a cell phone
When the robot user is done for the day, the logs on usage and errors can be easily collected by pressing a switch on the controller to put the Bluetooth in normal advertising mode. The company’s iPad can then connect to the controller and collect statistics to improve their reliability or other industrial operations.