lpcware

Connecting many LPC11C24s to CAN bus - ACK loading problem

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by LyraElectronics on Wed Feb 04 06:04:26 MST 2015
Hello all,

I have an application where strips of high powered RGB LEDs are each controlled by an LPC11C24, and they are all remotely controlled over a CAN bus.

At the other end of the CAN bus I have an LPC1768-based board with a TI transceiver to control all of the LED boards. There's proper termination at each end of the bus.

The problem I have is that as I add more boards into the daisy-chain of the CAN bus, I get more and more error frames.

Scoping this, it seems that the ACK signal gets stronger and stronger and pulls the levels of the CAN bus itself beyond its common-mode range.

I can prove it by pulling the STB high (to make them silent) on all the boards except the last one. When I re-run in this configuration I never see a single error frame.

Has anyone seen anything similar, or know how to overcome this without using an LPC11C14 + external transceiver?

Thanks,
Mike

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