Using a PCF8574 with Picaxe

[Keith Smith]

Hello, I have been trying to use a PCF8574 with an 18X, and having no success. I have found a page on the internet www.kranenborg.org/ee/picaxe/i2c.htm which certinally suggests that it can be done. At this point in time, I am wondering if I am driving ( Programming ) the 8574 correctly. I was wondering if anybody has achieved any results and if they could help me. Thanks.

 

[andrewpro]

I've had problems with the 8574 due to the fact that it's a 2 byte device (address and data). The picaxe prior to firmware 7.7 for the 28x and 40x, and somethin or other (the newest I beleive) for the 18x cannot do this with the I2C routines built in.

You can bit bang it jsut fine though.

 

[Technical]

You can use this with any X part by using the format

writei2c data1,(data2)

Also make sure you are using the right slave address in the i2cslave command - the A revision parts have a different slave address to the original parts (see the Philips datasheet), and you will also have to make sure the address pins match your slave address (A2 to A0). See the PICAXE i2c tutorial if you are not familiar with this.

 

[Immaculan]

Hi Keith,

I have started another thread regarding this topic. to do with using the PCF88574 to control a LCD.

Regards

Jamie