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I'm trying to intercept the signals between an old Elan uC and a HT-1622 LCD driver using a PIC18F14K50. There are 3 lines that are connected to the IOs of the uC: CS, WR(write clk) and DATA. At first sight it looks pretty simple, I just soldered 3 cables between the inputs on the HT-1622 and RB4, RB5 and RB6 on the PIC, and then I configured the registers like this: 

TRISB = 1;   // set all pins on port b as inputs
ANSELH = 0; // digital inputs
WPUB = 0;  // disable the pull-up resistor

The problem arises when the PIC is powered on, the LCD driver stops working as it should, and the signals I get on the PIC inputs aren't valid (they're always 1). Once I disconnect VCC on the PIC, the LCD Driver works again. So it seems I'm missing something, any thoughts?

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  • \$\begingroup\$ try using hex instead of decimal values for setting the bits, for example WPUB = 0x00 \$\endgroup\$
    – 1p2r3k4t
    Commented Nov 4, 2013 at 14:46
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    \$\begingroup\$ Yes, I ended using a binary value, but an hex value does the trick as well. Thank you! \$\endgroup\$
    – Hardy
    Commented Nov 4, 2013 at 14:49
  • \$\begingroup\$ you're welcome, there is another register that affects pull ups, option_reg, take a look if you want if you will need it in the future \$\endgroup\$
    – 1p2r3k4t
    Commented Nov 4, 2013 at 14:52

1 Answer 1

Reset to default
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TRISB = 1

This sets TRISB to 0x01: RB0 is input, all others are outputs.

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  • \$\begingroup\$ Wow! You're absolutely right, what a dumb mistake. You saved my day. Thank you very much! \$\endgroup\$
    – Hardy
    Commented Nov 4, 2013 at 14:47
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    \$\begingroup\$ Enlightenment comes from having been there ... \$\endgroup\$
    – Wouter van Ooijen
    Commented Nov 4, 2013 at 15:00

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