what's the difference between GPIO Expanders AW9523(product id 4886), PCF8575 (product 5611)

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quinn123
 
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Joined: Tue Oct 25, 2022 3:43 pm

what's the difference between GPIO Expanders AW9523(product id 4886), PCF8575 (product 5611)

Post by quinn123 »

Hi, Its a bit confusing to determine the difference between these two boards. If possible, from a practical standpoint, rather than from a pure hardware comparison whats' the difference? From a pure hardware comparison what is the impact of the difference features. From a simple question standpoint: Can both run a variety of sensors (infrared led (id 387) infrared receivers (product id 157),breakbeam sensors(id 2167).

The description for AW9523 says
The AW9523 is a twist on the common I2C expander:

First up, its very affordable - who doesn't love that?
It has 16 I/O pins, that'll double most boards' pin count
Four I2C address options, so you can connect 4 expanders to one bus
Each pin can be an input or an output
IRQ output can alert you when input pins change value
This chip does not support internal pull-ups or pull-downs, you will need to add an external resistor if you need one
However, it does have 8-bit linear constant-current LED dimming support so you can connect LEDs without resistors and have great looking dimming without PWM
The first 8 pins can be configured as open drain (as a group)


Whereas the description for PCF8575 says
First up, it's very affordable - who doesn't love that?
It has 16 I/O pins
Three I2C address select jumpers mean up to 8 expanders to one bus for 64 total GPIO added
Each pin can be an input with light pull-up or an output sink
IRQ output will automatically alert you when input pins change value
This chip does not have a pin direction register. You cannot set the pins as input or output - instead, each pin has two possible states. Basically, you can think of it as an open-drain output with a 100K resistor pull-up built in.
Option one: Lightly pulled up 'input' - by default it will read as a high logic level, but connecting the GPIO to ground will cause it to read as a low logic level.
Option two: Strong 20mA low-driving transistor sink output. This means the output is 'forced' to be low and will always read as a low logic level.


It seems that the PCF 8575 is more sophisticated with the ability to have light pull-up and output sink. One can't set the pins as input or output, but on the AW9523 one can set the pins for input or output, but not do internal pullups or pulldowns. Where doe these features come into play?

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bidrohini
 
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Re: what's the difference between GPIO Expanders AW9523(product id 4886), PCF8575 (product 5611)

Post by bidrohini »

Adafruit PCF8575 I2C 16 GPIO Expander Breakout - STEMMA QT / Qwiic has three I2C address select jumpers mean up to 8 expanders to one bus for 64 total GPIO added. It does not look like that the AW9523 GPIO Expander and LED Driver Breakout - STEMMA QT / Qwiic has this future.

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