| Touch button only need a pad on the PCB to be button, so it makes the button height nearly be zero. Without a traditional button's height and weight, touch button will help consumer product be slim and light, which is a trend of consumer products now.In available touch button detection technology, there is : Resistor Board sense (detecting the touch action by voltage change on resistor board), Electric field sense (detecting the touch action by electric field change) , and Cap Sense (detecting the touch action by cap change on button pad). In which the former two ways have weakness of high BOM cost and low design flexibility.It's a new technology of using CapSense theory to implement Touch Button detection, and there isn't any available or open solution now. It's said CapSense system once did by ASIC chips, but ASIC chips will have poor design flexibility. In my CapSense touch button system, by CapSense theory, I'll use a PSoC (Programmable System on Chip) chip to implement the system. The system will be low cost and has design flexibility, specially be easy to expand new buttons in the system, which should be proper for quick development in consumer products.In this thesis, first I'll analysis the CapSense theory, and introduce PSoC's structure. By CapSense theory, I analysis and design the system solution; use hardware resource in PSoC to design the hardware detection circuit , study and design the signal processing in the circuit. Meanwhile I design the software portion using PSoC's MCU core, including the system processing and how to make decision on touch action by detected data. By test result, I design the button size and PCB layout to get the best performance of CapSense, and show their relationship model with system output according to a lot of test data. Also I give my way of solving issues found in test, including noise issue, etc..Finally by real test and usage I verify the system, and have a simple study of the system's expanded usage on Slide or TouchPad. |
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