Lifelites LED's with PCF8574

[iplewis]

On PCB connector area, each item (ie 5 v) have two holes. Are they exactly the same and doubled for convinience?

It looks like it from the schematics. I suggest you check using a multimeter in 'resistance' mode.

When shortering jumpers should I solder together either 1 and 2 squares (for 0) or 2 and 3 squares (for 1)?

Yes, except that I think it's the other way around (1 & 2 = high ; 2 & 3 = low). Again, you can check this with a multimeter (in 'volts' mode, this time)

Also, I a bit confused with address. As I understood the address for PCF8574 is forming from the following combination:
S 0 1 0 0 A2 A1 A0 0 A. If A0-2 equal to zero the binary address is 01000000, which is equal to 0x40. If A0=1,A1=0,A2=1, the binary address is 01001010, which is equal to 0x4A. On I2C tutorial page I found that I should add 101 (0x05) to 0x40, hence 0x45. Please let me know which way is correct.

I think that the LSB (Least Significant Bit, i.e. the furthest right one) signifies whether the access is a read or a write. The page linked above (in h-g-t's post) suggests that the NBC functions set this bit automatically, so you can ignore it. So I think that your first suggestion is right: S 0 1 0 0 A2 A1 A0 0 A.

Cheers,

Ian.

[achechin]

Gents,
I assembled Mindsensors PCF8574 and its working ok. The only problem I realize after assembling is it size. To hide that plate required quite large area. So, the next step I am planning is to assemble custom PCF8574 and make it as small as possible.

I found a simple solution in "Extreme NXT" book.


Then compared it with schematic on mindsensor web-site.
http://mindsensors.com/index.php?module ... ile_id=844

It looks almost the same except switches to select the address. Here as I understood connet A0,A1 and A2 to 4.3V for 1 and to GND for 0.

The only question I have is why mindsensor use 1uF and 10uF capacitors? And what does two brown lines (8 GND and 16 VCC) means on schematic?