This project is the third variation of the theme "creation of RNG generators based on nuclear decay", you can find the other two implementations here:

NuclearRNG Version 1
NuclearRNG Version 2

This version, differently from the previous two, does not use a Geiger–Müller tube nor a classic Geiger counter but an array of PIN diodes produced by Teviso company, named BG51:

BG51 Datasheet

Using that component, the implementation of the present appliance is greatly simplified, avoiding all the high voltage circuitry necessary to operate a Geiger tube. Furthermore, the small dimensions of the component permits to implement a very compact device.

• A Raspberry Pico (RP2040) is employed as microcontroller platform;
• A BG51 radiation sensor;
• Some circuitry to filter the power source and to convert the logic level of the sensor output.

• As radiation source, a piece of ceramic coated with uranium oxide is employed. It comes from a salt / pepper dispenser I purchased set from the 50s, unfortunately one was damaged, the handle was broken and that peace is now temporarily the source of this appliance:

• A lead metallic shield contains both a radiation source and the sensor, fixed with non-permanent glue. The shielding has two functions, prevent radiation to reach the external environment and prevent external interferences, both particles (particle injection attack ? :-) ) and electromagnetic. In fact the product, as stated in datasheets, requires some kind of shielding:

• A circuit to stabilize input voltage is required, I tested also with boards different from Pico having the same results: being the sensor sensible to rumor in the power supply, a filter is mandatory. Testing without filtering in power input, produced distortions in the output. I implemented a filter using the specifications in Teviso's manuals and all problems disappeared.

• Datasheet tell us that at least 4V are required, so I opted for 5V and a small logic level converter to interface the sensor to Pico's 3V logic. This operation could be made with many different solution, I used my own.

• In loop, a register with a representation od an unsigned integer is cyclically increased from 0 to its maximum value, when it reaches the maximum it restarts from zero. When a particle is detected, the current value is stored in queue ready to be deployed on request;
• Default queue length is 10240 bytes.

• When a socket connects to the appliance via WIFI, a message with the following format is given as response:

ready\n

where '\n' is "newline" character

• You require a RN sending the message:

req

• Then you'll receive a RN in an answer with the following format:

<random_number><separator><generator_number><separator><available_numbers><newline>

where:

• the first field is a random number in the range 0-15 or the number 16 if an error was generated or no number is available yet;
• the second field represent the original value of the register incremented in loop to extract the random number using module operator of integer division by the specific range (0-255, 8-bit integers), it's provided as safeguard to verify that the loop cover every possible value for a given event frequency;
• the separator is the character ':';
• then a field with an integer telling you how many RNs are available in the appliance buffer, ready to be requested;
• a newline ( '\n' ) ends the message.

• Example:

52:3473460:1384\n

• You can terminate the connection with the command:

end

• At the moment, concurrent access is not supported (aka I don't need it for now), so, closing the connection also permits different client to connect;

• Raspberry Pi Pico SDK
• Cmake

Detailed instruction for dependencies installation are available on Raspberry website.

• Before compiling, is required to edit wifi_credential.hpp inserting Wifi SSID and password.

• compile the program as follow (set -DPICO_SDK_PATH using real pico-sdk path):

  cd build
  make -f makefile.srv all

• deploy the generated binary file named:

geiger_gen3.uf2 

putting the Pico in "deploy mode" pushing the white button before connecting USB cable and releasing the same button a second after the connection.

• A trivial Python client example is present in "test" directory in the present software distribution.
• The number can be requested from any program able to create Berkeley sockets using the described protocol.

• Thanks to Teviso company (https://www.teviso.com) that kindly provided the sensor for this project;
• Thanks to my friend Andrea ( https://github.com/btlgs2000 ) for his help to test this applicance.

• test and statistics