ESP32 DevKitJ (aka ESP-WROVER-KIT) - are some GPIO being pulled up to +5V??

MartyMacGyver
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ESP32 DevKitJ (aka ESP-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby MartyMacGyver » Thu Jan 19, 2017 10:18 am

I've been poring over the schematic for the LCD kit, and I notice that many of the GPIO I/O expansion connector lines have 10K resistors pulling them up to +5V:

https://dl.espressif.com/dl/schematics/ ... _SCH-2.pdf

But when I look at the board, it *appears* these are all unpopulated (I see solder bumps but no resistors or solder bridging them). In addition, there are 0 ohm "resistors" that appear to be present (not sure why both are in the design).

Why is this, and are the GPIO pins in question actually being pulled up externally at all by any of the remaining external components? Or was that just a late design change (because pulling up ESP32 lines to 5V appears to be a bad idea)?

(edited title to clarify the correct name of the ESP-WROVER-KIT)
Last edited by MartyMacGyver on Sun Jan 22, 2017 12:38 am, edited 2 times in total.

ESP_Sprite
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Re: ESP32 DevKitJ (aka ESP32-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby ESP_Sprite » Fri Jan 20, 2017 1:42 am

It was an optional idea the engineers had for some internal testing thing; I don't think we ever used it and iirc the new version of the kit won't have them anymore

MartyMacGyver
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Re: ESP32 DevKitJ (aka ESP32-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby MartyMacGyver » Fri Jan 20, 2017 9:16 am

New version, as in newer than what's currently shipping, possibly with the ESP32-WROVER on it? Cool!

I see pads but no resistors, so it looks electrically sound (no 5V pullups!) which was my main concern. Thanks for the info!

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krzychb
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Re: ESP32 DevKitJ (aka ESP32-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby krzychb » Fri Jan 20, 2017 10:56 am

On https://dl.espressif.com/dl/schematics/ ... _SCH-2.pdf schematic +5V GPIO pull up resistors are marked as "10K(1%)(NC)" and in green font.
There are couple of other resistors (including 0 oHm) marked with NC and green.
They are not not connected / not populated on my board as well.

MartyMacGyver
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Re: ESP32 DevKitJ (aka ESP32-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby MartyMacGyver » Fri Jan 20, 2017 11:42 pm

Ah! That makes sense, though I'm not sure why they're on there at all (perhaps the green elements mark late design changes). I'll watch out for that in the future.

ESP_Sprite
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Re: ESP32 DevKitJ (aka ESP32-WROVER-KIT) - are some GPIO being pulled up to +5V??

Postby ESP_Sprite » Sat Jan 21, 2017 1:45 am

In general, NC parts and 0-ohm resistor links are included when you're not sure what the level on the line needs to be, or if you want to have the option to repurpose the design without needing to spin a new PCB or manually solder bodge wires. You're right on the green bits; the black board you have is effectively the 2nd version; the 1st rev (iirc) was a limited batch of internal-only boards.

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