Whilst reading ST Application Note AN2548 "Using the STM32F101xx and STM32F103xx DMA Controller" I found the section 4.3 that describes the use of GPIO ports as a 16 bit parallel input which can be transferred by DMA to SRAM. See http://www.st.com/stonline/products/literature/an/13529.htm I have Fatar key board that is velocity sensitive. To scan the key contacts I need to scan 88 X 2 = 176 contacts. This can be done with a matrix of 16 X 12 = 192 leaving a few spare. It occurre