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opulo-inc / lumenpnp

The LumenPnP is an open source pick and place machine.
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Remove I2C MUX and use 2nd I2C Port for Vacuum Sensors #705

Closed KC0D closed 8 months ago

KC0D commented 9 months ago

Version Number

REV05

Bugfix or Enhancement

Enhancement

Description

The vacuum sensors use the same I2C address so a I2C MUX is used to address each one independently through a single I2C port. The I2C MUX is a fairly expensive part.

Suggested Solution

Remove the I2C MUX and use a second I2C port on the processor to address the 2nd vacuum sensor. I2C3 (PA8 & PA9) could be used for the 2nd I2C port. These pins are not currently used. Removing the MUX saves the cost of the MUX, plus five 10K resistors, two 4.7K resistors and maybe one .1uF cap.

Marlin would need to be modified to handle this new configuration.

stuartpittaway commented 9 months ago

I agree removing the MUX would be a benefit.

Unfortunately, Marlin has poor support for i2c as it currently stands - and expanding this to add a second i2c channel would require a lot of development work and testing in the Marlin code base.

There isn't a guarantee that the Marlin project owners would accept this change either.

sphawes commented 8 months ago

Yeah, unfortunately this is quite a thing to implement. For now, the mux is the simplest solution. I believe that's why we ended up choosing the mux to begin with. Unfortunately the vacuum sensor does not allow for selectable addresses, which would fix this issue as well.

Thanks for the thoughts @KC0D!