Esp32 issue

[abdi110]

I have a esp32 connected to my customized 7 segment and the power supply is 12 module connected to lm2596 to provide 3.3v power for esp32 , the 5 CAs pins of 7seg is connected to gpios of esp32 and cathodes of 7 segment are also connected to gpios of esp32 and multiplex the display the issue is when the esp32 is going to connect to the wifi modem the display blanks and has flickers, and every few second in wifi connection the blanking happens

 

[betwixt]

There will always be some delay in multiplexing when the cpu does other tasks but normally the WiFi runs on one core and user software on the other.
Do you have series resistors in the segment connection to limit the LED current? If not, you will be overloading the GPIO pins and that could be causing the problem.

For multiplexing I strongly advise you to use a timer to switch from one digit to the next, it will keep the multiplexing speed constant, no matter what other things are going on.

Brian.

 

[abdi110]

Yes I have series resistors and I use timer, as I understand the flicker is not about multiplexing it os about hardware because all digits blanks simultaneously and it seems the voltage is going low when esp32 communicate to modem

 

[pjmelect]

The ESP32 use a lot of current when it is transmitting, can your power supply, supply the required current and do you have sufficient decoupling close to the ESP32 chip?

 

[danadakk]

If you have a DSO just trigger at Vdd min needed, maybe 100 mV below that, and see if you get any triggers off
Vdd dropping too much. One shot mode would be handy. Se time/div around 1 mS for trial run. DC coupled
looking at Vdd.

The other thing you can do is DSO on infinite persistence, AC couple, say 100 mV per box, and see what pk-pk
noise you get. Its surprising on the ESP8266 and ESP32 modules what you get. Normal mode trigger, set trig
level at say 50 mV (to force it to trigger on most noise pulses).

 

[KlausST]

Thanks god someone invented schematics.

Klaus

 

[danadakk]

An example of simple server app on an ESP8266, noise due largely to xmit activity.

As you can see we easily get 200+ mV rail drops. This is with additional bulk C 10 uF, tant
on main board module plugged into. What you are seeing is 3.3V reg on module, and part
also driving, typically, one 10 mA LED. The "bursts" are the app on part going out to web to
get time of day.

 

[abdi110]

An example of simple server app on an ESP8266, noise due largely to xmit activity.

View attachment 199070

As you can see we easily get 200+ mV rail drops. This is with additional bulk C 10 uF, tant
on main board module plugged into. What you are seeing is 3.3V reg on module, and part
also driving, typically, one 10 mA LED. The "bursts" are the app on part going out to web to
get time of day.

YES i see the drops caused by bursts, the capacitors near esp32 didn't solve the problem,

--- Updated Apr 19, 2025 ---

If you have a DSO just trigger at Vdd min needed, maybe 100 mV below that, and see if you get any triggers off
Vdd dropping too much. One shot mode would be handy. Se time/div around 1 mS for trial run. DC coupled
looking at Vdd.

The other thing you can do is DSO on infinite persistence, AC couple, say 100 mV per box, and see what pk-pk
noise you get. Its surprising on the ESP8266 and ESP32 modules what you get. Normal mode trigger, set trig
level at say 50 mV (to force it to trigger on most noise pulses).

yes the bursts causes the voltage drops and tha blanking is because of these drops, capacitors didn't solve the issue

 

[danadakk]

Keep in mind cap ESR of course matters, polymer Tant best for bulk,
ceramic additionally helps with high freq stuff. The OS-CON below is the
poly Tant.

And of course C lead length L and trace L aggravate the problem.

 

[KlausST]

OP talks about a display... without giving any details
Brian talks about LED
But it could be LCD or VF or any other with or without driver....

For sure if using LED I won´t be surprised if the ESP outputs simply are not suitable to drive them. (current wise, as well as current_vs_voltage wise)

Klaus

 

[danadakk]

ESP32 more than enough current to drive LED segments :

Cumulative I/O max is 1200 mA.

 

[KlausST]

the 5 CAs pins of 7seg is connected to gpios of esp32

how much current is this when it drives an "8"???
less than 40mA?
still it has a drop down to 2.64V @ 40mA

***
and when I read 5CAs ... then I guess it´s 5 digits. means 35 segments plus the decimal points.

Klaus

 

[abdi110]

Dear all, I used a pnp transistor on each 5 pins of esp32 which drive the CA's of my LED 7SEG to amplify the current and it seems the issue is solved