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Problems connecting reliably via i2c to ADG728


I bought 6 samples of the ADG728 for switching microcontroller gpio's

I need to use 4 on the same i2cbus addressed as in documentation.

I soldered on bread board adapters properly and properly addressed them with a0,a1 connected to the gnd/+5V

I power them on the same supply as the microcontroller: 5V

I pulled up the scl/sda with different values resistors ranging from 1kR to 4,7kR to 10kR and even without (using internal pull ups of the atmel328pb)

I connected them together on the bus and interrogated them with the standard Wire library

I do not see obvious noise on the bus with the scope and neither i can properly understand why the device is not answering properly to basic connection  requests issued by a scanner.

(in the rare conditions when the chips answer i can send and see that the commands are executed )

I can not obtain a reliable connection to all of them ; meaning they sometimes respond they sometimes do not and never consistently... after a while 3 of them dissapear completly from the bus.

What i can do to diagnose and fix this ?

  • I also soldered the i2c connections on both the board and controller and they are near the controller 4|5cm

    When noticed that the devices with the A0A1 connected to gnd/Vcc I replaced them and improved stability a while then after fully connecting the rig and testing them a while i re-noticed  them disappearing from the bus ... now i remain stranded

    Would using them in a layout improve the chances of such erratic behavior?

    Please assist , i am on a really tight schedule and i need badly assistance!

  • Hi,

    Do you have a schematic of the configuration? Also, do you have scope plots of the digital signals you are supplying to the ADG728?

    The main debug considerations would be the correct digital signal is reaching the device and which is the quality of this signal.