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Muhh!!

From  the following relation we can calculate the unknown value of the internal pull-up resistor associated to a GPIO  pin that is configured as an input pull-up in the Arduino's sketch. 

I= (Vcc — Vfb) / R

having :

Vcc = 3.3V esp32 MCU power supply

Vfb =? V Forward V of the built-in LED 

I = 73.4uA measured LED current 

the calculated internal pull-up resistor value or magnitude is equal to:

R =  (Vcc — ?) / I

R = ((3.3 — ?)/73.4)*10^3 =  ?? kOhm.

I can't see image.

But it's not good approach for most applications since boost DC-DC converter and load will always drain battery.

1) XT1861B502MR-G (DC-DC IC)

From datasheet:

• 低静态电流：15µA
• Low quiescent current: 15µA

2) WS2812B-B/T (Addressable LED IC)

My measurements:

• Quiescent current: 720uA

3) SN74LV1T34DCKR (Level Translator IC for 3.3V -> 5V)

From datasheet:

• Static supply current: 1-10uA

That means (15uA + 720uA +1uA) ≈ 736uA will significantly affect on device sleep-mode current and to prevent additional power drain it should have additional switch.

Since typical system already has 3.3V switch and LED power relatively small it make sense to just connect boost DC-DC to it, instead of using additional switch.

I think powering boost DC-DC converter directly from battery would be a better solution then daisy-chaining one converter after the other

1. If powering from switching rail (like +3.3V_SW) — OK (because it will be disabled in sleep mode)
2. If powering from +3.3V rail — NOT OK, because it will cause significant additional current flow through resistor R1

That's why it's better to use two diodes and +3.3Vrail(you will save coin battery charge and power RTC from big battery)

Why can't I use the p-channel MOSFET solution if I am giving power from ESP32 and a 1.5V coin cell

humba humba bumba bumba kamba kamba

It's not my link, it's link where from I downloaded files. 

Backups available above of this link (Document + Gerber).

➡️ Source: https://drive.google.com/drive/folders/1WdWcisx70J... your zource is not working,please update,thank you

Great tip, just came across your site (now bookmarked) amazing and very helpful content, thanks for sharing.  I’d love to see more KiCad articles

Great. Thanks!

Is there a way to know how to do ADC sampling I tried to do something similar but the signal is lost and it is distorted a lot, will you have any suggestion to replicate something similar of your project ?

I would say up to ~700 kHz, if we talk about rectangular signal.

See the PWM-signal (50% duty cycle) chapter for more details with tests 10 Hz to 1 MHz.

What is maximum frequency it can measure accurately ?

Thank you! It was very usefull alhorithm to set hex-file generation until I closed my project, and then opened it again. Despite the fact that all necessary options have been selected (according items 4 & 5), project building creates *.hex.asm — file which contains two words: "; Disassembled code". There are no code errors (when build project), but working *.hex — file is absent. Please, help me to solve the problem!

Firstly open Device Manager (Win + R -> devmgmt.msc -> Enter) and check that your Serial Port is identified by the system.

If it's visible then check if any other software use it (like Terminal/Arduino IDE) and close it, because COM port cannot be shared.

Que hago si no me aparece ninguna opción de Serial port

Thank you for posting this. It has been very useful.

hi… thanks a lot… reading some comment from ST they suggest to calibrate the internal sensor of thje mcu. Did you do that? Thanks

Im using passive buzzer, everything is ok but buzzer sound is very very low, all i hear is clock tick sound. Then i check with another pwm input, it works fine. Is there anything i have to change? Im using official Nucleo f103rb

nice! thank you!