PCF8575 Does not work with my code....

[richard]

It makes no sense. From datasheet, page 7 and figures 6 and 10, seems that the 8575 can drive more than 25mA.

no , it can sink 25mA ,source 300uA

[Ioannis]

Correct! But what about the charts on page 7?

Ioannis

[CuriousOne]

I measured short circuit current of PCF8575 outputs. It is roughly 0.16mA.

[richard]

Correct! But what about the charts on page 7?

perhaps you should write to them , the graphs in figures 8,9 and 10 are questionable . perhaps the scale should be uA not mA

[Ioannis]

I measured short circuit current of PCF8575 outputs. It is roughly 0.16mA.

The ULN2803 needs at least 0.35mA, so practically 8575 cannot drive it with enough current.

perhaps you should write to them , the graphs in figures 8,9 and 10 are questionable . perhaps the scale should be uA not mA

Seems the datasheet has many errors...

Ioannis

[CuriousOne]

Yes it has problems pulling it up, but it has no problems pulling it down, so I added 2.2K resistor from input of ULN to +5V and now it can be controlled with PC8575.

[DaveP]

Unless you need I2C for comm, why not use something like a UCN5842 and run with shiftout? I have used these for at least 10 years...