RPi, ADS1115 shortage

[Jim Julian]

Hello,

   I'm building a data acquisition system using a Raspberry Pi, several ADS11115 cards and an MCP23017 I/O expander card.

The problem I've run into is this : the ADS11115 is limited to four cards in a daisy chain/cascade configuration. This leaves a maximum of 32 single-ended inputs or 16 differential inputs. 

   I need many more. I need, effectively, infinite expansion. I would settle for 128 differential input pairs. I'm not up on the i2c/smbus technology, but am wondering if the 16 extra expander pins can be setup as additional i2c ports. The MCP23017 expander card I'm using is limited to 128 extra pins, or eight MCP23017 cards.

   Has anyone come up with an addressing scheme that allows large numbers of devices to communicate on the RPi?

Thank you,

Jim J

[Andrew Scheller]

A) This group is virtually dead, if you haven't already, I'd recommend
asking your questions on http://www.raspberrypi.org/forums/

B) Here's some ideas anyway off the top of my head...
I don't think you'd be able to bit-bang additional i2c busses using the MCP23017
https://www.abelectronics.co.uk/ has some interesting stackable ADC cards
If you're 'naughty' you can use the ID EEPROM pins as an extra i2c bus
http://pinout.xyz/pinout/i2c
Some ADCs are available with SPI connections http://pinout.xyz/pinout/spi
I never looked in detail, but I remember seeing some "i2c expander"
boards mentioned on kickstarter
For truly large numbers of IO pins, I believe the usual approach is to
use an FPGA

Andrew

> --
> You received this message because you are subscribed to the Google Groups
> "Quick2Wire Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to quick2wire-use...@googlegroups.com.
> Visit this group at https://groups.google.com/group/quick2wire-users.
> For more options, visit https://groups.google.com/d/optout.