When this wemos S2 mini board isn’t connected to the AP, the LEDs flicker. No issue when the board connects to the usual wifi network. It opens its own AP when no wifi is found. I can’t pinpoint if it’s a power supply issue, or interference on the data bus.
I have 106 5v leds connected to the 5v line, about 90cm meter of strip. The ESP32 is mounted on a PCB with no traces or ground plane under the antenna, and a 10uf decoupling capacitor close to the ESP32 5v input. I’m connected to IO pin 5 with a proper level shifter. I’ve tried adding a 100uf capacitor to the power supply, which doesn’t help. Powering the board with USB, or a li-ion battery with 5V 2A boost circuit doesn’t make a difference.
reducing brightness doesn’t help.
I’ve connected the leds to a separate 5V lab supply and linked the ground to the ESP, the flickering stays. So that rules out power supply issues. The level shifter is still on the same supply as the ESP32, however. Can’t change that as easily.
The old flash method flashed it initially with WLED 0.14.4 , now I’m trying 0.15.0-b2 and 0.15.0-b4.
I’ve set the AP mode to open temporarily when the wifi network is not found. The device starts up, the AP appears on my wifi list for a minute. Then the AP goes away, but the flickering stays
At least initially, it doesn’t sound like a power issue.
What’s your “proper levelshifter” and how is it wired?
Have you tried any other GPIOs?
Do you get flicker during an effect or with just solid displays?
Have you tried reducing the number of LEDs that are lit? Try taking it down to 30 and see if that has any affect.
The levelshifter is with a VN2106 mosfet, the threshold voltage is low enough to work with 3v3 logic. 1k resistor on the gate, 1k resistor between the drain and 5v. The signal on my old analog scope doesnt look too great, a fair bit rounded off.
Flickering happens with 50 instead of the 144 leds as, with animation running.
No flickering when I run solid white on 140 pixels, but the 141th pixel lights up yellow somehow. Huh.
Ive reduced the framerate to 20 or 30fps, and the flickering is reduced a lot.
I tried pin 1 instead of pin 0, this makes the flickering even worse
The problem with trying to use something like a VN2016 is not only the voltage level to get it to drive (Vgs) but its switching speed which is related to the various associated capacitance values.
That MOSFET has some pretty high transfer capacitance values (220pf-900pf) which is not going to do anything good for the width of the 150ns pulses in the LED data stream.
I would strongly advise you eliminate the levelshifter variable by using a proper device. Until you do that, you’re very likely chasing a wide range of rabbit holes that may lead you nowhere.
I’m a big fan of any of the 74AHCTxxx devices. They’re cheap, simple, need only a single 5V supply and are well proven.
thanks for the thorough feedback. I got some SN74LVC2T45’s through Digikey. used one on a breakout PCB and perfboard, the scope signal is looking great. the flickering is reduced a lot, but not entirely gone.
I added a 100uf capacitor to the 5V supply, close to the LED strip, which doesn’t help. I also got a few other IC’s, like SN74AHCT125DR. I guess I can try those, use a separate power supply for data and the ESP, etc…
I have access to a digital oscilloscope with storage function, I should have a look at it.
