I have successfully controlled a PCF8574A 8 bit I/O expander chip via i2c via a Picaxe in regards to its inputs and outputs. But when I try to send an output from one PCF8574A to an input to another PCF8574A it doesn’t seem to work.
If I take one of the inputs and tie it directly to +5v it will report it as such when I do a read (i.e. %00000001). But even when I measure +5v on an output pin from another PCF8574A and try to connect it to that same pin (with the +5v connection removed of course) it reports that there is no input signals. (i.e. %00000000). It also looks to be the same if I try to give it a high from a TTL 74LSxx chip as well, no input signals detected.
And yes, they all have the same common ground.
Edited by - erdc on 16/02/2007 16:18:19
If I take one of the inputs and tie it directly to +5v it will report it as such when I do a read (i.e. %00000001). But even when I measure +5v on an output pin from another PCF8574A and try to connect it to that same pin (with the +5v connection removed of course) it reports that there is no input signals. (i.e. %00000000). It also looks to be the same if I try to give it a high from a TTL 74LSxx chip as well, no input signals detected.
And yes, they all have the same common ground.
Edited by - erdc on 16/02/2007 16:18:19