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LDR0 and LDR1 with a single pushbutton switch


We are building a PCB using the G120 chip, and got a question about the LDR0 and LDR1 pins.
Can I safely join the two pins together, let them float (no pullup to high) ?
And when I would need to upgrade the firmware, I ground them both together (using a pushbutton switch for example)?

The reason why is that we just want to expose a single switch outside the enclosure when a firmware update is necessary.

I already tested the method and it works with the G120HDR, but just want to confirm if it’s an OK solution or if it’s hack that may or may not work in the future.


Looks ok to me


Can I safely join the two pins together, let them float (no pullup to high) ?

I believe the pullups are already on the G120 module.



Cobra II schematics suggests the same.


Thanks for the help!


You are welcome!


What about if you need to go into Tinybooter mode as LDR0 needs to be high and LDR1 low?


Could happen, but normally you use the G120Updater from GHI once the GHI bootloader is installed.
Seems like a safe design step.


Yes this is how I intend to update the firmware: using the GHI updater.
Thanks for all the feedbacks


Not being able to get into TinyBooter mode may cause a problem in the future with SDK version upgrades?


I think it is alright. Not recommended but in worst case you can enter GHI loader, load tinybooter only without firmware and run teh device. IT will boot in tinybooter :slight_smile:


Hey just to say that so far the solution works.
I press the LDR0+LDR1 as a single switch, reboot the device (either reset or plug and unplug) and I can update the firmware.
This is on our new custom board using the G120.


Can you share details about your product?


And some photos please :smiley:


This is for monitoring and data acquisition of industrial machines.
I will give more info once we have everything all sorted out :slight_smile:

But here are some teasers:

Mainboard Features:
-Power over ethernet
-LCD touchscreen
-Soundcard speaker+mic

input of wide range (7v to 280v DC/AC)
output of wide range (0-280V AC/DC 12a)


Nice! I love that we’re seeing more commercial products posted here lately. :smiley:


Please share with us. Maybe we can post on showcase as well, like this one


@ PhilM - Great looking device!