Atmel QTouch Library User Guide

can beconfigured asYb Lines)SMP Yes Yes Yes YesThe configurability is provided to select X,SMP and YA lines on Same Port ,X,SMP andYB lines on same port.Number of X ports should be 1 means the X lines should be connected to a single port.Note: YA and YB cannot be on the same port.SMP Pin should be less than equal to 19 th pin of any Port.Checklist of items for integrating QMatrix Capacitive sensing librariesWhen integrating QMatrix acquisition method libraries, ensure the following• Check that the CLKPR register is available for the selected device. If not remove theCLKPR statements.• Ensure that the configuration for the QMatrix is done in touch_qm_config.h and thearrays of the x_line_info and y_line info are filled as indicated section 5.8.2• MCUCR register is available and if so disable pullups• Check if the timer registers and bit fields used are correct and change them if necessary.• The above settings can be modified by the user by changing the API’s that are availableto the user. The API’s includeo qt_set_parameters ( )• The host application must provide the current time.This information is passed to the library as an argument to the functionqt_measure_sensors()”. This is used for time-based library operations such as driftcompensation.• The GPIO internal pull-ups must be disabled for all port pins used for touch sensing whencalling the library.For 8-bit AVR devices, this can be done byb. Setting the “PUD” bit in the “MCUCR” register orc. Setting the “PUD” bit in the “SFIOR” register.• Setting the JTD bit in the “MCUCR” register to disable JTAG Interface in MCU ( ifavailable ). This can be done only when the JTAG lines are in conflict with the desiredtouch sensing lines.• The library must be called often enough to provide a reasonable response time to usertouches. The typical time to call the library is from 25 ms to 50 ms.• Care should be taken while using the ADC conversion logic and QMatrix library such thatthe host application waits for approximately 1msec before actually calling theqt_measure_sensors() API depending upon the ADC clock.Common checklist itemsConfiguring the stack size for the applicationThe stack requirements for the QTouch library should be accounted for and the stack sizeadjusted in the user’s project for proper operation of the software when using the IAR IDE. Thissection lists the stack usage for the different variants of the QTouch and QMatrix acquisitionmethod libraries applicable to the IAR compiler tool chain.67