ESP32 won't boot with some TFT display parallel

Projects General Guidance
1

Hi,
I'm getting a very strange problem.
I'm using an ESP32 DEVKIT V1 and a 3.5" TFT Display shield (so it is 8-bit parallel), which works absolutly fine with this configuration (yeah it is platformIO but the problem is not the code I think):

	-DTFT_CS=33
	-DTFT_DC=15
	-DTFT_RST=32
	-DTFT_WR=4
	-DTFT_RD=2
	-DTFT_D0=12
	-DTFT_D1=13
	-DTFT_D2=26
	-DTFT_D3=25
	-DTFT_D4=17
	-DTFT_D5=16
	-DTFT_D6=27
	-DTFT_D7=14

The strange problem is that with this display (ILI9488) the ESP32 boot up normally without any problems:

blue_display
blue_display1920×1440 223 KB

But with the same wiring and same ESP32, if I connect this other display, the ESP32 won't boot up unless I disconnect the D2 pin. As soon as I disconnect the D2 pin the ESP32 will automatically start without any reset needed. Then I plug back the D2 pin, press reset and the display will work untill I unplug the ESP32 from the USB power (I will need to repeat the process). This is the problematic display:

red_display
red_display1528×988 264 KB

Am I missing something? on the internet I didn't find much about this problem.

Thanks!

2

Plugging and unplugging when the power is on can damage or even destroy circuits.
Posting the datasheet links for both the displays would give us a fair chanse to find out.

3

I'm really sorry, but I couldn't find any datasheets for these two displays despite my search. Many Chinese versions are available, but most lack documentation. I also checked in my eBay orders, opened the product page, like the one for the red display (TFT Display), but no datasheet was provided.

The only file I could find for the blue display is the datasheet attached here, though it’s not an exact match for the board. Additionally, I found some websites linking the red display to the same datasheet I’m attaching.
Website for the blue board: Interfacing 3.5 INCH TFT Display Shield with Arduino - Electropeak
Webiste for the red board: Interfacing 3.5 INCH Full Color Touch TFT Display Shield with Arduino

3.5inch_Arduino_8BIT_Module_MAR3501_User_Manual_EN.pdf (1.0 MB)

4

That's bad. As I have no experience of any of them I'm out.

Can't You settle for the one that behaves itself?

5

I could, but the red one had some burnt pixels that just so happened to be covered by an image, so I thought it would be a missed opportunity to hide them xD

Also the red one has a brighter display than the blue one.

Anyway thanks for your time Railroader, maybe someone else can help us?

6

The D2 pin has special requirements in down load mode. Its state should be immaterial in normal boot mode. You may want to check how D2 is connected on the two boards to see if there is a difference.

https://docs.espressif.com/projects/esptool/en/latest/esp32/advanced-topics/boot-mode-selection.html

7

Reading the doc you shared Boot Mode Selection - ESP32 - — esptool.py latest documentation

It says:

GPIO2 must also be either left unconnected/floating, or driven Low, in order to enter the serial bootloader.
In normal boot mode (GPIO0 high), GPIO2 is ignored.

It says that the D2 is ignored in normal boot mode. Maybe I should try pulling it down? Or maybe I'm not in normal boot mode.

I know that for pulling down I have to connect the D2 to GND with a resistor? Am I right? and which Ohm should I use?

8

Aha, I understand. If no other reply solves the matter, can You buy a new, exact same display?

9

Checking the wiring with both display, I see that D2 is not changing his resistance with the GND pin on the display board.

10

That is why I said it should be immaterial. But there is something different about between the two boards. That is why I said to check and see h0w it is connected on the two boards.

11

My Bad! I checked again with the multimeter. On the blue one (the working one), there is a 10K resistance between D2 and GND. On the red one, however, I get O.L. when the positive lead is on D2 and the negative on GND. If I reverse the leads, I measure 1.2M Ohm.

So I could safely try attaching a 10k resistor between the two pins?

12

I assume O.L. is an open circuit? Adding a 10K resistor shouldn't hurt anything. Give it a try and see if it helps.

1 Like
13

Yey! it works!

14

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