Codes and Data for the Exposure Notification on the Raspberry Pi. Exposure Notification Service, previous is called Contact Tracing, is named by Apple and Google in their documents. The code here implements the Bluetooth Specification from Apple and Google on Raspberry Pis which run Debian-based systems.

Before running the code, some libraries are needed for Raspberry Pi. Note that bluepy is used in Python 3.

$ sudo apt-get install python-pip libglib2.0-dev
$ sudo pip3 install bluepy

I may forget some libraries I installed. I will check the above list again.

Next, the bash script (.sh) needs to be executable. To achieve this, run

$ chmod +x ContractTracing_BLE.sh

Finally, run the bash script by typing $./ContractTracing_BLE.sh

Done!

Note: Remember to change the Rolling Proximity Identifier (RPI) for each device. It can be changed in ContactTracing_BLE.conf file. If you clone the code to multiple devices but forget to change it, all the records will have the same RPI. But you can still identify different devices via MAC address.

The program records the information of other BLE devices that use the same service (the Exposure Notification Service). The output is in a .csv file. The format of the csv file is as follows.

The first column is the Unix Time and its unit is second. The second column is the MAC addresses of the other BLE devices. The third column is the received RSSI (dBm). The fourth column is the Service UUID, and it is 0xFD6F for the Exposure Notification Service. The fifth column is the Rolling Proximity Identifier (RPI), which can be seen as the unique ID of each device. The sixth column is the version of the service. Currently it is 0x40. The next column is the transmit power level (dBm). The hex value 0x0C is 12 in decimal. So it is 12dBm. The last column is reserved for future use. The detailed information about Service UUID and RPI can be found here.

I have found that the first error usually comes from the Python, i.e., the scanning function. The error code is

bluepy.btle.BTLEManagementError: Failed to execute management command 'scanend' (code: 3, error: Failed)

By checking the bluepy source code, the error is from Line 854 to Line 803 to Line 312, and it occurs when running scan.stop().

My current solution is to reset the BLE by using sudo hciconfig hci0 reset when the error happens. It looks that this action fixed the problem and the BLE can run again.

There are some possible solutions for this issue (by searching the Internet):

1. The problem may be caused by using the Bluetooth and Wi-Fi at the same time, since two modules are in one chip. This may be the case since I found that if I disconnected the VNC (remote access), the two RPis could communication again, even though one of them was dead hardly.

2. Power supply. Since the BLE chip will consume more power. But I do not quite believe this.

4/28 Update: After fixing this by resetting the BLE, the devices run at least a whole day. However, after analyzing the collected data, I found that there is a chance that two devices can't see each other for at most 14 minites (which occurs once in an 18 hours continuous running). Not sure if this happens due to the BLE problem or other issues.

1. Revise config file so that both bash script and Python can read and import it.
2. Change to the absolute path or current path.
3. Add function to log the fail events.
4. Removing the judgment of Var1, which is from ... 0x00a 00.
5. Analyze the probability that the scanning can't find all the other advertisements. BTW, make a slide drawing the timeline with advertising and scanning.
6. Integrate the Cryptography Specification from Apple and Google. Currently, the Rolling Proximity Identifier (RPI) is static and I just write some random numbers for it. The Metadata (including Version, TX power, and Reserved) is not encrypted.
7. Figure out how to change the MAC address to the random non-resolvable address. Not sure if Raspberry Pi allows doing so.

1. Change to the new Apple-Google message format.