Programmable Pocket Calculator Hardware Description This programmable pocket sized calculator has the following features: Credit card size, 8mm thick! ARM Cortex M4 Microcontroller microSD card reader OLED Display 44 mechanical* matrix keyboard (*tactile switches) Lipo battery charging circuit Images Unsoldered, showing it's thickness Soldered Front view of PCB without tactile switches and with OLED in place Back view of PCB unsoldered with battery, micro usb and micro sd card reader in place Altium's 3D Render of the PCB