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NXT + PCF8574 
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squiggy
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Joined: Fri Apr 20, 2007 3:22 am
Posts: 36
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Well, if those pins are grounded you're ok. You can test that with a continuity detector. I had to add solder. It's possible they changed their design though. They changed from the PCF8574 to the PCF8574A without changing their documentation.
Thu Jun 19, 2008 2:49 am
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docilio
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Joined: Sun Sep 09, 2007 10:12 am
Posts: 116
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squiggy wrote:
Here's a picture, hope it's not too large

http://home.comcast.net/~squig/pics/pcf8574-nx.jpg

The sample I posted in this thread should work. There's a header and then a sample program.

Are you trying to output or input?


Input... my problem is that i only got the PCF8574, not all that circuit...
i will try it any way... code and idea...

Thanks

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Thu Jun 19, 2008 5:55 am
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docilio
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I have conections like these:

G |01......16| VDD (5V)
G |02......15| Resistor to 5V and SCL from NXT
G |03......14| Resistor to 5V and SDA from NXT
Switch |04......13|
|05......12|
|06......11|
|07......10|
G |08......09|

This works with 04 pin (the code 0xFF)

what codes should i use to 05 to 07, and 09 to 12
what msg should i send to light a led on in another place?

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Thu Jun 19, 2008 7:02 am
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squiggy
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Posts: 36
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So take a look at your chip, is it labeled

1. PCF8574

2. PCF8574A

?

There's a difference in the base address

The PCF8574A is 0x70
The PCF8574 is 0x40

If you have the PCF8574 the header file of the sample code I gave would need to be changed to

Code:
typedef struct{
   byte i2cMessageSize;
   byte i2cDeviceAddress;
   byte i2cWriteMessage;
   } i2cBlock;

i2cBlock PCF8574A_I2C;
byte PCF8574AwriteMessage = 0;
tSensors PCF8574Aport;

void setupPCF8574A(tSensors setPort)
{
   PCF8574Aport = setPort;
   SensorType[PCF8574Aport] = sensorI2CCustomFast;
   PCF8574A_I2C.i2cMessageSize=1;
   PCF8574A_I2C.i2cDeviceAddress=0x40;
   PCF8574A_I2C.i2cWriteMessage=0xFF;
}

void writePCF8574A(byte mess)
{
   PCF8574A_I2C.i2cMessageSize=1;
   PCF8574A_I2C.i2cDeviceAddress=0x40;
   PCF8574A_I2C.i2cWriteMessage=mess;
   PCF8574AwriteMessage = mess;

   if (nI2CStatus[PCF8574Aport] == NO_ERR)
       sendI2CMsg(S1,PCF8574A_I2C.i2cMessageSize,1);

}

int readPCF8574A(byte ioMask)
{
   byte value[1];
   PCF8574A_I2C.i2cWriteMessage=0xFF;
   PCF8574A_I2C.i2cWriteMessage=PCF8574AwriteMessage|ioMask;

   if (nI2CStatus[PCF8574Aport] == NO_ERR)
       sendI2CMsg(PCF8574Aport,PCF8574A_I2C.i2cMessageSize,1);
   wait1Msec(20);

   if (nI2CStatus[PCF8574Aport] == NO_ERR)
      readI2CReply(PCF8574Aport, value[0],1);

   return (int)value[0];
}


Pins A0-A2 would be connected to your ground.
Thu Jun 19, 2008 4:41 pm
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docilio
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Posts: 116
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PCF8574AN

not working... =(

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Thu Jun 19, 2008 6:15 pm
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squiggy
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Joined: Fri Apr 20, 2007 3:22 am
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OK,

so Im not sure which address you would have, I suspect ox70, but first you need to check to see if the device is working.

try using from the sample programs:

NXT Scan All I2C Add.c

It should tell you if it's working or not.
Thu Jun 19, 2008 6:58 pm
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docilio
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Posts: 116
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hi all

in Input mode, everything working now...

a few questions...:

how to get ask a singular bit? (know if P0 is 0 or 1)
how to set a port as 0 or as 1 ? (Output)...

I wanna light a led on P1, how to control it?

I don't know what to send on "write to" function

Thanks

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Thu Jul 03, 2008 3:51 pm
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docilio
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Posts: 116
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Ford Prefect wrote:
hi,
in our German forum we have a member who wrote a program with this PCF to connect a small keypad to the NXT:
http://www.mindstormsforum.de/viewtopic.php?t=2885

foto: Image

HTH!


Hi, i saw the code of that, but as it is explained in german, i didn't understand what codes use to the OUTputs

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Thu Jul 03, 2008 3:58 pm
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docilio
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I did it =)

I Finally did it =)

Sorry about all problems that i give to you,

Now i can put a LDR, 2 Leds, and 2 Buttons...

I will later on try put some old SRF-04 working on that PCF...

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Thu Jul 03, 2008 6:51 pm
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