OBDuino Mega

[dcb]

lcd_gotoXY probably needs a tweak for 4x20 to get the lcd addressing right, here is the original 2x16 version
/*
* LCD functions
*/
// x=0..16, y=0..1
void lcd_gotoXY(byte x, byte y)
{
byte dr=0x80+x;
if(y!=0) // save 2 bytes compared to "if(y==1)"
dr+=0x40;
lcd_commandWrite(dr);
}

[jonoxer]

Originally Posted by dcb

if(y!=0) // save 2 bytes compared to "if(y==1)"
dr+=0x40;

Oh yeah, that's the problem right there. It assumes that if it's not the first row it must be the second.

Thanks DCB!

I'm running in 16x2 mode at the moment but once I've finished mucking around with the datalogging and GPS code I'll have a look at that.

Cheers :-)

Jonathan Oxer

[jonoxer]

I've fixed the lcd_gotoXY function so it works correctly with 20x4 displays, but at the cost of an extra 54 bytes. That's a lot of extra memory for something that not many people will want, so maybe there should be two versions of the function and the correct one is selected at compile time based on the value of LCD_ROWS.

This is the new version of the function:

void lcd_gotoXY(byte x, byte y)
{
  if ( y > LCD_ROWS )
    y = LCD_ROWS - 1;    // Safety check for calls beyond the LCD

  byte row_offsets[] = { 0x00, 0x40, 0x14, 0x54 };
  byte dr=0x80+x + row_offsets[y];

  lcd_commandWrite(dr);
}

8 bytes of that extra volume is the check for calls to a row beyond that allowed for the given LCD size. Without that check in place it's possible for a call to this function to read random memory beyond the end of the offset array, and send that data to the LCD.

This function can probably be optimized but it's working fine for me on a 20x4 and since I'm running on an ATmega1280 with 128K of memory the size doesn't really matter to me. If someone else wants to have a go at putting it on a diet, go for it!

[nickdigger]

here you go:

//byte row_offsets is unused
byte dr = 0x80 + x + (y&1 ? 0x40 : 0) + (y&2 ? 0x14 : 0);
//32 bytes saved (burp)


edit: this one appears to save 18 more:

byte dr = 0x80 + x;
if (y&1) dr+= 0x40;
if (y&2) dr+= 0x14;

[Froggy]

Thanks for the hard work guys. I log in to see what's up and see some great looking code already posted.

Using Nickdiggers code, it only costs 4 more bytes. (Zero increase for two line displays if we exclude the second if statement.) Very nice.

[jonoxer]

nickdigger, you're a champion.

byte dr = 0x80 + x;
if (y&1)  dr+= 0x40;
if (y&2)  dr+= 0x14;

Tested on my 20x4 and works perfectly. I've committed that to my copy of the OBDuino32KMega tree.

Cheers :-)

Jonathan Oxer
http://jon.oxer.com.au/

[Froggy]

I have checked in the revised OBDuino32k code that allows 4 line displays to function correctly. (version 165)

Thanks to all involved in the correction.

[Froggy]

That's quite the impressive Google Earth display. There's a lot of potential there.

[jonoxer]

Thanks Froggy.

I did a blog post about it on Practical Arduino yesterday, too:

Practical Arduino: News - Car engine datalogger project update

I ran the logger again this morning on my trip to work, and now that I have everything in place it only takes a few seconds to plug in the memory stick, run the conversion script, and open it in Google Earth to see a trip visualization. This morning I had a few work colleagues looking over my shoulder as I flew around the trip and they thought it was pretty cool.

Cheers :-)

Jonathan Oxer

[Mesuge]

Thanks for this fantastic addition to the OBDuino project.
You might be interested in connecting those three buttons wirelessly via
basic strap on style steering wheel remote kit, in that fashion you can easily cycle through the different PID and contrast settings on the LCD and still be safely focused with both hands on driving.

some links:
steering wheel remote - Google Search