More Hitachi LCDs With The PIC 16X84
In a previous post, I discussed how to use the Hitachi LCD’s four bit mode. However, sometimes you need to save a few more I/O lines so you might consider the circuit presented here
In this case, a 74164 serial-to-parallel converter is used to hold the data to be sent to the LCD. Since only two pins are required to shift the data out (one to shift out the data, the other to provide a clock), two I/O pins are saved at the expense of one additional chip in the circuit. However, using the serial-to-parellel converter limits you to sending data to the LCD. You cannot read data back as you can with the previous circuit. The routines used to access the LCD using this interface work the same way as for the first interface and are available here.
Finally, in the June 1994 issues of Nuts and Volts magazine, Karl Lunt presented a circuit using a 74595 serial-to-parallel converter that cuts the number of I/O pins needed to just two. Intended for use with the SPI interface on the Motorola 68HC11, I don’t see any reason it couldn’t be adapted for use with the 16X84. For back issues, contact Nuts and Volts at:
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