Note there is a semi-completed Manual for the design attached which explains the circuit (its a zipped PDF)
This is an update to my original 2015 design, based on a new customer who wanted a 868Mhz LORA compatible system. The changes are:
The BOM Cost still well under US$100 including:
a) The membrane keyboard ($7ea zipped PDF overlay engineering drawings attached) b) The MT700PA 3.3V 2D Barcode module ($30ea) and C) The custom cut case. This is based on the 1357025mm szomk 2xAA battery holder plastic handheld enclosure with transparent front. if you order a MOQ of 50 you can specify the cutouts for the LCD and keyboard cable
The test firmware is also attached (As a Microchip MPLAB-X Project). This is work in progress as the client is doing most of the software design but does cover power management, keyboard, LCD, barcode, RFID reading and sending out a test message. There are plenty of public domain libraries for using the RFM95/RFM69 modules.
|4x4 Keyboard Overlay Engineering.zip|