Designing a USB Keyboard with the Cypress Semiconductor ...

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Designing a USB KeyboardFoundKey1 ms ISRKey =KeyCodeTable[Column][Row]Clear Watchdog TimerCompare row bit withKeySwitchImage[Column][Row]3 ms ofbus inactivity?YesSave GPIO Portsettings. Write ‘0’ toColumn port bits.Key statusPressedReleasedNoKey is amodifier?Key inDebounceFIFO?NoYesNoEnable GPIO interrupts(falling edge) on Port 2Suspend until busactivity resumesYes Key ==LastTx?NoDisable GPIO interrupts.Restore port settings.YesPhantomkey situation?Yes1Set TxRequiredflag to TrueHas 4 mspast?YesSet Task to SCAN_TASKNoDebounce_FIFO[Debounce_Pointer]=KeyNoSet TxRequired flagto TrueKey is amodifier?YesSet TxRequiredflag to TrueSet ModifierByte in FIFOHas 12 mspast?YesIncrementDebounce_PointerNoNoLastTx = Key1Debounce_FIFO[Debounce_Pointer] =Illegal matrix indexEP1 FIFOfull?YesFill EP1 FIFO with01H (Rollover Error)NoAdd Key to EP1 FIFOReturnReturnFigure 24. FoundKey RoutineFigure 25. 1 ms ISR12
Designing a USB KeyboardGPIO ISRBus is stillidle?NoYesSend Remote Wakeup signalReturnConclusionFigure 26. GPIO ISRThe two main enabling factors of the proliferation of the USBdevices are cost and functionality. The CY7C63413 meetsboth requirements by integrating the USB SIE and multi-functionI/Os with a USB optimized RISC core for a low price perpart.© Cypress Semiconductor Corporation, 1997. The information contained herein is subject to change without notice. Cypress Semiconductor Corporation assumes no responsibility for the useof any circuitry other than circuitry embodied in a Cypress Semiconductor product. Nor does it convey or imply any license under patent or other rights. Cypress Semiconductor does not authorizeits products for use as critical components in life-support systems where a malfunction or failure may reasonably be expected to result in significant injury to the user. The inclusion of CypressSemiconductor products in life-support systems application implies that the manufacturer assumes all risk of such use and in doing so indemnifies Cypress Semiconductor against all charges.
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