code for qt60161
This is not a simple question, you must specify what be a month quantity, if you will make 3 keyboard per month is one's, if you will make a 100 or more is other one. What is for you low cost, the cost is directly connect to the quantity. What be a product, what must be a exterior of the keyboard. Very easy construction you can see below, but the cost is not lowest, this is suitable for low series. Another way is using keyboard like in a mobill phone or calculators, you will have a sensor's pad on your pcb and must buy the keyboard, you can buy it from many different place. Other choice is using the flat printed keyboard, many companys manufacture a standard configuration.
About C source, how many key will have the keyboard and how will be organized the key, for example if you have 12 key, the can be in matrix 3x4, 4x3, 6x2, 4x4 ....or directly 12 outputs ....