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Topic: 3 wire SPI, HD44780 and 74HC595 Toggling 595 Pins 14/Q0, 2/Q2 (Read 509 times) previous topic - next topic

transcendtient

I've setup my Teensy 2.0 with the configuration and code found here http://playground.arduino.cc/Main/LiquidCrystal#Information.

I'm trying to find a solution to use the other two pins not used by the LCD on the 74HC595 to toggle some solid state relays.

My final product will be on an ATTiny45 and I want to leave the other three pins on the Tiny available for future possible functionality.
I'm open to looking at other libraries since I'm pretty sure this one doesn't have that functionality.

transcendtient

I've found a workaround with the library.

Modify the LiquidCrystal.h by making the _bitString variable and spiSendOut() functions public.
Code: [Select]
public: uint8_t _bitString; //for SPI  bit0=not used, bit1=RS, bit2=RW, bit3=Enable, bits4-7 = DB4-7
  void spiSendOut();      // SPI


Then by setting the value of bitString and sending it you can set the register values; 1 = q0, 4=q2, 5=q0+q2

Code: [Select]
lcd._bitString=VALUE;
lcd.spiSendOut();


This is really useful of you don't want to waste those pins on your 74HC595!

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