LED1642GW - No data output on SDO

[GKerwood]

I have a project whereby I intend to cascade 13 LED1642GWPTRs, in order to control a number of RGB LEDs.

As an "in-progress-check", I have currently placed only two LED1642GWs, each as the schematic below, with SDO of the first chip connected to SDI of the second. I have verified that the CLK, LE and PWCLK are common and within specification, also that the chips are powered and grounded. IMPORTANT: I have yet to connect any loading LEDs so as such, all OUTs are open (NC).

I wanted first to check for cascading operation, however I have found: Data is only output from the SDO of LED1642GW Number 1, when there has been a digital key passed on LE. No data is "pushed through" otherwise. Specifically, if I serialise 2 16bit words to Chip 1's SDI, I would have expected the first word to have cascaded through, however, nothing at all is output.

My thoughts are that either the chips are in an error state given that the loads are open or I have misunderstood something fundamental about their operation. I would greatly apricated some support.

Many Thanks

[GKerwood · Accepted solution]

I was undecided whether or not to delete this question given the answer, perhaps an admin/senior community member could advise?

The reason for this was signal degradation on SDI. I had been running my SPI data through an AND gate in order support another active low input, however the transistors I had chosen clearly weren't up to the task. Working with a logic analyser and not a scope, I hadn't realised the issue. Direct input from the SPI had the chip responding as expected.

Sorry!

[Peter BENSCH]

Thank you very much for the feedback that it finally worked!

There is absolutely no one here in the forum who has not learned by making mistakes. Isn't troubleshooting one of the most interesting things and the joy all the greater when you have found it?

In my opinion, your question should not be deleted because it may well be a recurring problem with other users as well. So if you agree to leave it in the community, I'll be very happy to mark your answer with Select as Best.

Thank you again for the nevertheless very interesting question!

Regards

/Peter

[GKerwood]

Thank you, Peter, much apricated :) It was certainly a head scratcher not really having the equipment or experience to find the issue!

Kind Regards