PCF8574 I/O board

[VK5ZAG]

I recently fried the chips in an I/O board.
These have been replaced.
The PCF8574 fails to respond
Another board has been constructed.
It behaves the same??
I have 3 of these boards.
One working OK with NX chip.
2 not working with Philips chip.

I am being convinced that the Philips chips are either
faulty or substantially different.

Can anyone comment on this?

[Sid Boyce]

Difficult to say but it is possible. One way would be to use a scope or
multimeter to check both under the same conditions and compare the results.

I had a problem with RX/TX switching on the UHFSDR with the AS157's that
were shipped as part of my kit.

I struggled with it for nearly a year until I bought some AS169's and
replaced the AS157.

The datasheet said they were logically and physically the same, but they
were definitely not.
73 ... Sid.

--
Sid Boyce ... Hamradio License G3VBV, Licensed Private Pilot
Emeritus IBM/Amdahl Mainframes and Sun/Fujitsu Servers Tech Support
Senior Staff Specialist, Cricket Coach
Microsoft Windows Free Zone - Linux used for all Computing Tasks

[Mike Collins]

Hi Eric,

The only thing I have seen is when you use a 8574A..... the A version
has a different fixed address. If they
are all 8574's then I am not sure what is happening.

73, Mike Collins KF4BQ

[VK5ZAG]

Thanks Mike,
After the ritual putting on of the spec's I found that the
required chip is the PCF8574AT (with the specs I could read
that on the fried chip) The replacement I used was PCF8574T
The addressing for the 8574A was 57 and this by my calculation
would translate to 33 on the 8574. However I get no response?
Ordered 5 ATs from China and will see how they Go.

Best Regards 73 Eric VK5ZAG

[Sid Boyce]

That would be 39 hex.
73 ... Sid.

[VK5ZAG]

Thanks Sid.
I have tried to get MoBoControl5 to address the chip
but with no success. 33 and 39 no Joy.
I suspect the firmware will not allow addressing
of the low address chip. I have ordered some
PCF8574ATs and will wait for the slow boat from
China.

Best Regards 73 Eric VK5ZAG

[f6itu]

Hi

If the reference sufix is "AT" on both devices, there is definitely no difference between NXP and Philips I.C.'s (as NXP is the new brand of Philips Semiconductor). I've 3 or 4 years old protoboards of the filter switching unit using Philips devices, and I'm using now NXP ICs without caring of anything special.

 

Most of them have been bought @ Farnell, some NXP branded one coming from China via eBay.

73'

Marc

 

 

[Mike Loebl]

Sorry chiming in late...  I did the original PCF8574 board design, and there was a big with the boards that the address jumpers were placed upside down from the board layout.  Not sure if that helps or not.

-Mike

KB1MTS

 

 

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[VK5ZAG]

I am aware of the address junpers.
I have three boards.
One is AOK with 8574AT
the other two are not addressed
I used 8574T and address is lower.
I think MoBoControl5 will not
accept the lower address of 33
instead of 57.
I have ordered the 8574AT chips.

Best Regards 73 Eric.