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Hardware stack.
A diagram of the wiring.
The microcontroller and its components. This SIM card has 500MB of data, and ten years of service with a one-time payment.
Some components are connected via female jumper cables to male pins; others I soldered together. All of the wires had to be trimmed, stripped, twisted, soldered for reinforcement, and insulated with heat shrink.
The two devices assembled and working.
A rendering of the 3D printed case.
Bit of software.
The OLED screen cycles through these messages.