#26 Write to LCD changes PIO.X-status

v1.0x_(future)
closed
owlib (16)
5
2014-09-04
2007-02-05
Proquar
No

Using the LCD_H-tree of owfs I should have Pins 0-2 for free use. For reading a button-state PIO.X should be 0. But when i do a
echo 1 > LCD_H/clear
or a
echo test > LCD_H/screen
owfs changes the PIO-states to 1.

On the other hand when I do
echo 0 > PIO.0
there appear some strange characters on the display.

Discussion

  • Tiger
    Tiger
    2014-09-03

    There is no solution possible due to hardware restrictions.

    The hobbyboard uses the RSTZ pin (#10) of the DS2408 to create /STROBE output signals on any write access to the chip. The LCD will read the port output from the DS2408 as soon as it receives a /STROBE signal, regardless of wheter the signal was created by a port pin change to either pins 0 to 2 or pins 3 to 7.

    It follows, the pins 0 to 2 can only be used as inputs, but not as outputs, because any time one of the pins is set by, e.g. echo -n 0 > PIO.0, the automatically by the DS2408 generated /STROBE signal will cause the LCD to malfunction.

    I suggest to change the status of this issue to rejected or unresolvable.

     
  • Paul Alfille
    Paul Alfille
    2014-09-04

    • status: open --> closed