Sure, there are several materials which could help,including: schematic, codes, documents.
You could download all the materials in following links.
GM-V1.1:
Materials DIY Geiger Counter Kit-v1.1:
GeigerCounterSMT-V1.2 which is proper for geiger counter Integrated module in your system:
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geiger-counter with Atmega328P Nano OLED and AA battery case
https://github.com/2969773606/geiger-counterNanoOLED
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GeigerCounter-V0.8 materials ：
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Make one GeigerCounter Server using Raspberry Pi:
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More materials for related developing kits:
ManualDigitalGeigerCounter:
IOT Opensource Weather Station: