Re: [lcd4linux] HD44780 I2C driver issue

[Michael R. <mi...@re...>]

Hello Laurent,

Although I never owned nor used a HD44780-i2c-display, I had a quick look at the sources: i2c should support 
"Soft-Wiring", this menas you shouldbe able to specify the signals in lcd4linux.conf

But I don't know the syntax :-) just try some of the examples from the normal wiring, usind onnly DB0..DB7

try to strat lcd4linux with -fvv, ond look in the output for occurences like

	info("%s: wiring: [DISPLAY:%s]<==>[i2c:DB%d]", Driver, name, w);

the soft-wiring code is in drv_generic_i2c.c, function
unsigned char drv_generic_i2c_wire(const char *name, const char *deflt)


good luck! :-)


Am 2014-04-07 16:22, schrieb Laurent HAAS:
> Hi all
>
> I'm currently trying to use lcd4linux on a WR703N router with OpenWRT,
> with a 20x4 HD44780 LCD equipped with an I2C interface.
>
> Unfortunately, after several hours of struggle, I finally found that the
> I2C integrated (soldered) interface -  model YwRobot LCM1602 - is
> finally not compatible with the plain HD44780-I2C driver :-(  I got the
> same behavior as the TRAC ticket #295 described.
>
> These LCD + interfaces are sold by many vendors (mostly Chinese etc.)
> and under several brands.
>
> Actually, the 4 bits of data are assigned to the 4 HIGHER bits of the
> "abstracted Port", and RS, RW, and EN are assigned to the LOWER bits :-(
>
> Here is the corresponding table between the PCF8574 output pins and the LCD
>
>      PCF 8574         LCD
> Pin  Function   Pin  Function
> 4      P0        4      RS
> 5      P1        5      RW
> 6      P2        6      EN
> 7      P3        NC (backlight ?)
> 9      P4        11     D4
> 10     P5        12     D5
> 11     P6        13     D6
> 12     P7        14     D7
>
>   From what I read on the HD44780 wiki page, in 4 bits mode, the data
> bits are ALWAYS assigned to DB0-DB3, and it seems there is no way to
> assign them to DB4-DB7 (which in turn are always assigned to control
> signals).
>
> Can you help ?
>
> Thanks !
>
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-- 
Michael Reinelt <mi...@re...>
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