2020/11/11 18:04:49
Corvachip
Hi,
I am trying to add multiple IOs to my circuit using the MCP23S18, have anyone tried to daisy chain this chip? Looking at the datasheet I don't see a way to do it but probably someone in the forum has tried it. This will save me from using a ChipSelect for every chip.
 
Thanks
 
 
2020/11/18 00:30:44
Mysil
No,
The SPI variant of the device have a 'Control Byte' similar to the I2C device,
But there is No ADDR pin, so there is no possibility to select a different address for each device.
 
You may possibly use a 3 to 8 decoder external to the microcontroller, or an external shift register,
to expand the number of CS lines.
 
    Mysil
2020/11/18 00:53:10
ric
or use the I2C version of the chip, so you CAN have multiple addresses on the same bus.
 
 
2020/11/18 01:41:01
oliverb
The pin-out looks almost identical to the MCP23S17, which does support addressing. Of course that has push-pull GPIO instead of open drain. The advantage of open drain appears to be that you can pull the pin up to 5V even if the VDD pin is a lower voltage. -edit- but if the whole thing is 5V powered you could probably get away with using the MCP23S17 and emulating open drain by writing zeros to the output latch and controlling it through the TRIS bits.
 
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