Re: [Lcd4linux-devel] display on WRAP-Board - how fast is i2c?

[Luis C. <lfc...@lf...>]

Stefan Krister wrote:
> Hi all,
>
> success!
>
> I have blinking LEDs at the pcf8574 output lines while lcd4linux is
> running! My LCD is still 'dark' but that may be a other problem ...
>
> I'm not 100% sure, but i think, that
>
> insmod scx200_acb.ko base=0x810,0x820

  Yes, that was it!

  That is why the module we use was modified in the first place. For 2.4
  kernels there was no useable module, hence the need to modify it.

  I now also have my I2C module working as well, and this time also
  powered by 3.3V, it's blue backlight module i salvaged from an old HP
  printer (HD66710). Pity it won't do any lowercase characters...

  I will need something in the lines of a uppercase_all plugin or
  something similar, that would produce proper text output (everything
  written in CAPS). Michael, any hints on this?

  Stefan, i'm also finetuning the driver a bit, try this attached file,
  where i did some minor changes and bug fixes.

Update, sf.net is forbidding .ZIP file extensions, so i'll just copy 
past my changes here.

CHANGELOG:

drv_generic_i2c.c:

The exit code was not done properly.
p.s. there is still a need to properly detect the I2C slave device, 
which i'll do in some days along with the extension for full 8bit mode 
using two PCF8574. This is of course just a plan, knowing my previous 
time-to-market failed objectives :P

drv_HD44780.c:

The second delay for 4.1ms was wrong
4bit and 8bit code decision and initialization needs to be done also here.


------------------------------- CUT HERE -------------------------------


drv_generic_i2c.c:


int drv_generic_i2c_open(const char *section, const char *driver)
{
     int dev;
     char *bus, *device;
     udelay_init();
     Section = (char *) section;
     Driver = (char *) driver;
     bus = cfg_get(Section, "Port", NULL);
     device = cfg_get(Section, "Device", NULL);
     dev = atoi(device);
     info("%s: initializing I2C bus %s", Driver, bus);
     //info("device %d", dev);
     if ((i2c_device = open(bus, O_WRONLY)) < 0) {
			error("%s: I2C bus %s open failed !\n", Driver, bus);
			goto exit_error;
     }
     info("%s: selecting slave device 0x%x", Driver, dev);
     if (ioctl(i2c_device, I2C_SLAVE, dev) < 0) {
			error("%s: error selecting slave device 0x%x\n", Driver, dev);
			goto exit_error;
     }

     info("%s: initializing I2C slave device 0x%x", Driver, dev);
     if (i2c_smbus_write_quick(i2c_device, I2C_SMBUS_WRITE) < 0 ){
			error("%s: error initializing device 0x%x\n", Driver, dev);
			close(i2c_device);
		}

     return 0;

   exit_error:
     free(bus);
     free(device);
		close(i2c_device);
		return -1;
}


drv_HD44780.c

	change init sequence around linen 995 to this:

     /* initialize display */
     drv_HD_I2C_nibble(allControllers, 0x03);
     udelay(T_INIT1);		/* 4 Bit mode, wait 4.1 ms */
     drv_HD_I2C_nibble(allControllers, 0x03);
     udelay(T_INIT2);		/* 4 Bit mode, wait 100 us */
     drv_HD_I2C_nibble(allControllers, 0x03);
     udelay(T_INIT1);		/* 4 Bit mode, wait 4.1 ms */
     drv_HD_I2C_nibble(allControllers, 0x02);
     udelay(T_INIT2);		/* 4 Bit mode, wait 100 us */
     drv_HD_I2C_command(allControllers, 0x28, T_EXEC);	/* 4 Bit mode,\ 
1/16 duty cycle, 5x8 font */


------------------------------- CUT HERE -------------------------------

Have fun.

If I can, i'll prepare a small webcam video to illustrate how slow the 
I2C bus can be, speccially with scrolling widgets like 'OS'.

Luis Correia


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