hallo du nase...
ich habe gerade deine frage gelesen und habe mich da an etwas erinnert. also habe ich in mein archiv geklickt und die gewünschten informationen gefunden.
ich hoffe du kannst ein bisserl englisch... und du verstehst was der verfasser meint, dann wirst du diese schaltungsvariante lieben. es ist zwar ein 4x4 ... aber das kannst du ja leicht abwandeln.
der vorteil gegenüber vielen anderen lösungen ist die interruptsteuerung. das heisst, dass der mikro nicht immer schauen muss, ob einer ne taste drückt oder nicht.
falls jedoch einer eine drückt, wird er durch nen interrupt aufgescheucht und versucht rauszufinden, welche taste es war.
hier mal der text des autors, den ich leider namentlich nicht nennen kann:
und dann die zeichnung. lass dich von dem verwendeten mikrokontroller nicht stören... ports sind ports... int eingänge sind int eingänge!Code:The third method, an interrupt-driven keypad, offers several benefits. First, using interrupts frees the microcontroller to perform other tasks or to switch into an idling or power-down mode while awaiting the next key closure. Second, using interrupts helps reduce electromagnetic interference produced by continuously scanning the keypad's lines. Figure 1 shows an interrupt-driven keypad implementation that's based on Atmel's AT89C52 version of the popular MCS-51 family of microcontrollers. Here, the rows of a 16-key keypad, S1 through S16, implemented as a 4×4-key matrix connect to the lower nibble (P1.0 to P1.3) of IC1's Port 1. The keypad's columns connect to IC1's Port 1 upper nibble (P1.4 to P1.7) and a network of four diodes (D1 through D4 and a 10-kΩ resistor, R9. The junction of R9 and the diodes' anodes connects to Port Pin 3.2 and generates an interrupt whenever the user presses a key. Initially, Port 1's lower nibble sits high at logic one, and the upper nibble is grounded at logic zero, applying reverse bias to the diodes and pulling the signal high. Pressing a key applies forward bias to the diode corresponding to that row and causes to go low, generating an external interrupt to the microcontroller. Upon receiving an interrupt and after a 20-msec software-debouncing interval, the microprocessor sequentially reads the row and column lines. Capacitor C1 provides a hardware-based debouncing interval of approximately 25 msec. In this design, the microcontroller's software returns a binary-formatted input corresponding to the pressed key's number as sensed at Port P1 (P1.0 to P1.3). As the commented assembly-language routine, available here, explains, the software ignores invalid key combinations. Idle and power-down modes available in CHMOS (complementary high-density MOS) versions of the MCS-51 family save power and thus make these microcontrollers ideal choices for battery-operated devices. For example, a 5V, 12-MHz Atmel AT89C52 consumes approximately 25 mA in active mode, 6.5 mA in idle mode, and only 100 µA in power-down mode. Any enabled interrupt can switch the microprocessor from idle to active modes.
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