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Hi,everyone Are you using a keyboard management IC? Which one is the best? Take 4 X 4 keyboard for a example! Discuss it!
hi, no way to discuss it. Use port0: 4 bits as output and 4 bits as input (do not forget to add pull-up resistors for last ones). If you search for keyboard management IC especialy then there are some x51 MCUs with such option, for example Atmel's AT89C51RB2/RC2 - they have built-in Keyboard Interrupt Interface. Good days!
But if a additional IC is ued,the port could be saved. Now,I'm using a ZLG7189 which is produced by Guangdong Zhouligong in China.It has a I2C-like interface. Only 4 port line is used and tow of them could be shared. And it could scan keyboard automatically,in fact,it could manage 64 keys and 8 7-seg LED. Maybe others are using a better IC.If you let the MCU scan keyboards,it will also take much CPU time.
hi, If you let the MCU scan keyboards,it will also take much CPU time Here it is implemented via 1/50s interrupt and takes about 30 assembly commands with total time about 20mks - 0.1% of processor time (= good days!