Points to Note when Designing Touch Switches 1 Points to Note when Designing Touch Switches Points to Note for Routing Points to Note for Using the Software Package Points to Note for the Using e-Link 2 Points to Note for Routing Materials Routing Grounding Interface Reservation 3 Points to Note for Materials PCB Materials Single, double, multiple layer PCB or FPCB Board Materials Isolating materials such as ABS plastic, glass, acrylic etc. Electrode Materials Metals such as PCB copper plating, springs etc. Electrode Shape Round, square, polygon etc. Board Platinoid PCB Routing Board Metal Spring PCB Routing 4 Layout Notes The routing of the Touch IC power (VDD, GND) must be independent. The power lines must be decoupled with filter capacitors (e.g. 0.1uF, 10uF) before reaching the IC. Maintain a ground plane for the power lines if possible and have the GND routing area > VDD routing area. The touch key routing should be managed first and should be kept as short as possible. The distance between two linked routings should be double the wire width. Touch keys related to different touch modules (ex. key1 and key5) should avoid parallel routing. The touch key routing should avoid high frequency signal lines or be separated with a ground wire. The touch key routing should use as few through holes(Via) as possible. 5 Points to Note for Grounding Grounding – dual or multi layer applications Top layer : Solid grounding for the outer PAD (using a gap of 0.508 mm from the PAD) Bottom layer : Ground net below the PAD (using a wire width of 0.18 mm with a 1mm grid point spacing) Unit : mm 1 mm = 39.37 mil 6 Interface Reservation Reserve the ICP or I2C interface in advance Reserve the ICP interface : For on board writing and sensitivity adjustment Reserve the serial communication interface : For signal detection Reserve I2C interface : parameter adjustment and signal detection ICP, I2C Pin-out 7 Points to Note in the Software Package Software Package Operating Flow System Parameter Configuration Software Package Resource Configuration Software Package Parameter Adjustment Software Package Procedure Adjustment ★ Check databook for details 8 Software Package Operating Flow Power on Initialization _SCAN _TOUCH_KEY =0 _SCAN_CYCLEF =1 _GET_KEY_BITMAP Key pressed ? =1 Key function =0 Cycle ended 9 System Parameter Setting IC Select System Frequency Setting Select which part no. IC to use Both BS83 and BS85 are available The default system frequency software setting is 8MHz 8 / 12 / 16MHz are all available I/O or Touch Key Setting Most I/O ports are pin-shared with touch key input pins Only Input or Output or touch inputs can be selected 10 Software Package Resource Setting Software Package Resources in use ROM : 1.2k word (Fix) RAM : 1 Key × 12bytes Interrupt : Time base (Fix) Specific Registers : MP0, MP1, IAR0, IAR1, BP Stack : 3 layers 11 Software Package Parameter Adjustment Software Package Parameter Adjustments Sampling Time : Longer sampling times will result in improved key discernments Maximum On Time : Prevents keys from remaining in an erroneous touch status Calibration Time : Time setting for environmental calibration Debounce Times : The touch key decision time One Key Active : Only one key will be accepted at any time Key Threshold : The touch key sensitivity setting 12 Software Package Program Calling The time to call the signal procedure “_SCAN_TOUCH_KEY” Time to read the key value The _SCAN_TOUCH_KEY procedure must be called from within the main program and not from within a subroutine so as to prevent stack overflows. After each “key-scan” cycle is implemented, a signal bit “_SCAN_CYCLEF” will be generated which means the actual key output value and also the time needed to read it. User Configuration It is necessary to return to the main cycle after the key value has been issued and the corresponding function has been executed. To avoid single loop delays that will influence the response speed of the touch key. 13 Points to Note when Using the e-Link Programming Function Power supplied by the e-Link and the target board power supply must be removed before programming. Parameter Adjustment The power supply can be selected using the HXT Editor configuration to be sourced from the e-Link, 5V or 3.3V, or from an external supply. Signal detection - Power isolated mode When signal detection is executed, the target board power can be chosen to monitor real signals. 14