Firmware Scan

Firmware scan is a method for pin-testing microcontrollers with a special firmware that is uploaded to the flash or SRAM that will start a state machine that is similar to Boundary Scan.

This process is not patented, so please feel free to replicate.

Functional description: firmware_scan.pdf

First make sure it is worth doing. If the device already has Boundary Scan, then you don't need this. If the port you are using to program the flash is also a debug port, that allows you to read from the GPIO registers, then you don't need to do this. I have found that the most useful application for Firmware Scan was on PIC12/16/18, AVR devices (formerly Atmel) A166 micros by ST and Infineon.

If you can find a free downloadable compiler that will allow you to write simple programs in assembly code, that is all you need. If the circumstance requires the purchase of an expensive development suite, then it might not be worth your while.