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G120 - side effects when LDR0 and LDR1 are wired together?


#1

We did a redesign off a custom board and have some strange problems with the SD / USB client.
One off the changes between the previous version is that LDR0 and LDR1 are hardwired to one button instead off 2 separate buttons.
Could this have a impact? Anyone did this before?


#2

We have wired them together also.
I haven’t seen any issues I would relate to this.
Our board also has SD, USB Host, USB Client (for update/debug only), ENC28.
The attached image shows how we do it.
The right side goes to the G120.


#3

Hello Reinhard may you explain why so much components? Is it for protection purpose?


#4

@ Reinhard Ostermeier - Thanks, it was a long shot but you never know…
Have you seen the behaviour in the screenshot before?

This is with the SD card mounted to the USB client.


#5

Hey, don’t ask the software guy :snooty:

In fact I have no idea.
But since we expose the LDR_1 pin to an external connector, I guess it’s for protection.

p.s. Secretly I believe my HW college had fun filling his 1st 4 Layer board with life :whistle:


#6

As mentioned above we use the USB client interface for update/debug only.
But I had a lot of strange issues with SD card after write access.
The problem is that NETMF caches a lot of write operations to SD card, and when you reset too early, the file or even the whole folder in which the file is located gets corrupted.
Because of this I rarely write anything to SD.

I also blame a lot of timeouts/long running operations to the “Ghost breakpoints” (Execution suddenly stops when VS debugger is attached).
But when running without debugger this can not be blamed.


#7

Yes, that is what it looks like.

The diodes prevent the voltage going above the 3.3V rail or below the 0V rail. The resistor and capacitor do a little low pass filtering to prevent some switch bound being passed to the input. Good design practice, give your hardware engineer a pat on the back.