ESP32 Forum

Posted: **Mon Apr 01, 2019 9:52 am**

Hello !

I'm trying to use a SMD 2727 P5 64x32 LED Display with the ESP32. I've opted for the following library https://github.com/NeoCat/ESP32-P3RGB64x32MatrixPanel

I've soldered the wires for the default constructor.

I've passing the wires through 2 Level Logic Converters, from 5V to 3.3V.
These are the specs of my power supply:

https://i.postimg.cc/prt2vnW7/20190401-145102.jpg

As you can say I don't use GPIO 1 and 3, which are UART 0 TX and UART 0 RX respectively.

But I can't upload a sketch while the ESP is mounted on the board and connected to the Power Supply. I have to take the ESP out and upload a sketch than put it back in.

How did this happen ?

I am sure I soldered the wires as it says in the above mentioned library.

Thank you !

Posted: **Mon Apr 01, 2019 10:59 am**

Check at least GPIO12 - that's a bootstrap pin and if it's at the wrong level, the upload will fail.

Posted: **Mon Apr 01, 2019 11:02 am**

ESP_Sprite wrote: ↑
Mon Apr 01, 2019 10:59 am
Check at least GPIO12 - that's a bootstrap pin and if it's at the wrong level, the upload will fail.

Check how ? With what ? What should I see ? How does the wrong level look like ? Or the right level ?

The GPIO 12 is connected to a Logic Level Converter and then to A pin on the HUB75.

Posted: **Wed Apr 03, 2019 4:49 am**

Well, one thing to check is what happens if you disconnect it. If it works then, GPIO12 is the issue.
The right level: It Depends. GPIO12 sets the voltage for the internal flash depending on the level it sees on boot-up: high = 1.8V, low = 3.3V. I'm not sure what devboard/module you use, so I can't say which flash level you need, but it's usually 3.3V. In that case, what you need to do is to measure if your logic level converter happens to pull up that pin to a high level. If it does that, there's your problem.

(Also ref https://github.com/espressif/esptool/wi ... -Selection )

Posted: **Wed Apr 03, 2019 9:31 am**

ESP_Sprite wrote: ↑
Wed Apr 03, 2019 4:49 am
Well, one thing to check is what happens if you disconnect it. If it works then, GPIO12 is the issue.
The right level: It Depends. GPIO12 sets the voltage for the internal flash depending on the level it sees on boot-up: high = 1.8V, low = 3.3V. I'm not sure what devboard/module you use, so I can't say which flash level you need, but it's usually 3.3V. In that case, what you need to do is to measure if your logic level converter happens to pull up that pin to a high level. If it does that, there's your problem.

(Also ref https://github.com/espressif/esptool/wi ... -Selection )

Hello ! Thank you for your answer.

I am using a ESP-Wroom-32: https://i.postimg.cc/mg8nNsDD/20190403-121636.jpg

I've connected the 3V3 of the ESP to the OE and VA pins of both Logic Level Converters that I've used to shift 5V to 3V3.

https://i.postimg.cc/8CWNycr4/20190403-121832.jpg

That is one of the LLC I used.The VB was connected to the Power Supply and the VA was connected to the 3V3 of the ESP, and as I mentioned above, to the OE pin as well.
So on the VB side of the LLC I went with wires to the HUB75 and on the VA side I went to the ESP32 pins.

Code: Select all

+---------+   Panel - ESP32 pins
|  R1 G1  |    R1   - IO25      G1   - IO26
|  B1 GND |    B1   - IO27      GND  - GND
|  R2 G2  |    R2   - IO21      G2   - IO22
|  B2 GND |    B2   - IO23      GND  - GND
|   A B   |    A    - IO12      B    - IO16
|   C D   |    C    - IO17      D    - IO18
| CLK LAT |    CLK  - IO15      LAT  - IO32
|  OE GND |    OE   - IO33      GND  - GND
+---------+

I followed this guy's library: https://github.com/NeoCat/ESP32-P3RGB64x32MatrixPanel

And he used GPIO 12, and it worked for him. That's why I never looked twice when I used GPIO 12.

Later EDIT: Here is a schematic to the board:
https://i.postimg.cc/PxXHWhh6/Schematic ... 160858.png

Posted: **Tue Apr 09, 2019 4:44 am**

d12 needs to be left open or pulled low at start up assuming your powering your board with 3.3v
I would imagine the input of the converter it connects to must be hi z so that should be ok.

read about all the strapping pins here:
https://github.com/espressif/esptool/wi ... -Selection

Posted: **Wed Apr 10, 2019 9:23 am**

axa88* wrote: ↑
Tue Apr 09, 2019 4:44 am
d12 needs to be left open or pulled low at start up assuming your powering your board with 3.3v
I would imagine the input of the converter it connects to must be hi z so that should be ok.

read about all the strapping pins here:
https://github.com/espressif/esptool/wi ... -Selection

I've tried connecting the board to the PC using only a USB Cable and then I've connected GPIO 12 to a GND pin and the 3V3 pin and nothing happens.

The thing must be broken.

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[SOLVED] Can't upload sketch on ESP32 while it's connected to board

[SOLVED] Can't upload sketch on ESP32 while it's connected to board

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