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RE: P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

michaelkellett — Fri, 20 Feb 2026 10:14:43 GMT

You have about 50uA leakage through the MOSFET when it's supposed to be turned off - the spec says it should be less than 1uA.

Try shorting the MOSFET gate to source (I know its already meant to be at the same voltage but maybe that only happens when your meter is there - I have seen that before.)

Then check that it really is turning off.

Also try a restive load rather than the ESP32.

I have seen a batch of MOSFETs that were a lot leakier than spec - so it could just be that.

P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

arvindsa — Wed, 18 Feb 2026 05:49:18 GMT

I’m using a DMP2045U P-channel MOSFET as a high-side switch to control 3.3V power to an ESP32-S3-WROOM module. The gate is driven by an STM32.

Connections

Source → 3.3V (measured 3.289V)
Drain → ESP32 3V3 pin
Gate → STM32 GPIO
10k pull-up from gate to 3.3V

Measurements

When gate is LOW (~0.009V):

Source = 3.289V
Gate = 0.009V
Drain = 3.289V
Vgs ≈ −3.28V → MOSFET turns fully ON (as expected)

When gate is HIGH (3.287V):

Source = 3.289V
Gate = 3.287V
Vgs ≈ 0V → MOSFET should be OFF

However:

Drain measures ~2.89V

I added a 47k pulldown resistor from drain to GND. This reduced the drain voltage to ~2.4V — but not to 0V.

All STM32 GPIOs connected to the ESP32 are driven LOW.
If I completely remove the MOSFET, the ESP32 3V3 rail stays at 0V (no floating voltage).

Question

Is this expected off-state leakage/floating behavior for a discrete P-MOSFET in this configuration, or is there something wrong with my circuit?

RE: P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

Jan Cumps — Thu, 19 Feb 2026 22:42:55 GMT

Is it possible you have active signals on the digital lines when the ESP32 is off, that seep to the power rail?

RE: P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

kmikemoo — Thu, 19 Feb 2026 19:48:04 GMT

And sometimes, they just leak. Either way, the solution is the same; replacement.

RE: Woohoo!! My first chip antenna PCB design works successfully!

arvindsa — Thu, 19 Feb 2026 16:16:21 GMT

Thank you so much. Even though the competition is over, i always make attempt a new feature in all my project, in a way it does not hamper the core functionality. just to learn about implmenting it. Plus i Ain't leaving Any project incomplete unless absolutely necessary.

I was sure of getting the NRF to work, but chip antenna and to get two nrf to sync was my learning objective.

Woohoo!! My first chip antenna PCB design works successfully!

arvindsa — Thu, 19 Feb 2026 05:29:34 GMT

For my Hack the Holidays, i was trying to make a Christmas tree Earring. It did get stuck in for almost an eternity, but it did arrive, Then i kept it procrastinating because i was working on my Connect 4 Game. But yesterday, when i set up my soldering station (I have a tiny room so its a portable setup) i decided to solder the earring too. Now, this was the first time i am making a PCB with a chip antenna. In my Light Up your life, i managed to make a Inverted F antenna, but there i had the liberty of the PCB size. This one, the PCB is small like around 40x20mm, so it had to be chip antenna. I had many NRF52832 and chip antennas in my drawer which i bought and never used. I was fighting against many factors that can make the PCB not work -

Old components may not solder well
Incorrect Design of Matching network components
Incorrect PCB Routing including deviation from the 50Ohm Impedance.
ESD Damage
Random Silly mistakes from my end.

This is a two layer board and based on Kicad's impedance calculator i had used nearly a 3mm wide track for the 50Ohm impedance path. In Hind sight thats half the size of the NRF52 Chip itself.

But Against all odds. one of the boards worked unconditionally. The second was not showing up the BLE beacon. It was a example program from Nordic. But assuming a cold solder, i took it to my university and blasted them with hot air to flow them with a good flux and boom.. The beacon worked. I got a more than 10m range with them. That's the farthest i could go without losing Line of sight in the room. Was so excited that i had to share this.

Now on to more things..

RE: Woohoo!! My first chip antenna PCB design works successfully!

JoRatcliffe — Thu, 19 Feb 2026 16:09:29 GMT

Well done continuing to work on this project and nice PCB design 🙂

RE: Woohoo!! My first chip antenna PCB design works successfully!

arvindsa — Thu, 19 Feb 2026 15:06:50 GMT

Let me not tease you, here is the full PCB Design along with the inspiration i took from www.etsy.com/.../christmas-tree-earring-laser-cut-file

RE: Woohoo!! My first chip antenna PCB design works successfully!

arvindsa — Thu, 19 Feb 2026 15:04:37 GMT

I thought due to minor mismatch in the network, i will get some 4~5m. But i am getting double that. So i just copied the design from
https://devzone.nordicsemi.com/f/nordic-q-a/100062/nrf52832-with-chip-antenna the only difference was that the reference design was for 4 layer PCB, mine was 2 and so had to use a 3mm thick trace.

So more than my skill, it is more of my luck that it turned out well..

RE: Woohoo!! My first chip antenna PCB design works successfully!

dougw — Thu, 19 Feb 2026 14:35:11 GMT

Cute PCB...

RE: Woohoo!! My first chip antenna PCB design works successfully!

Oliver2003 — Thu, 19 Feb 2026 06:49:53 GMT

That is fantastic news! Getting a chip antenna design right on the first try is no small feat—RF layout can be so tricky. It's such a great feeling when the signal comes through clean and strong. Great job sticking with it!

I'd love to know: how is the signal range looking compared to your expectations? Did you have to do much tuning on the matching network?
Also, here are some resources that you'll love to read as a beginner in the PCB:
https://learn.sparkfun.com/tutorials/pcb-basics/all

RE: P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

arvindsa — Wed, 18 Feb 2026 06:32:19 GMT

I had simultaneously soldered two boards. Using standard reflow profile on miniwares hotplate, yet both showing same behaviour. I will try replacing it.

RE: P-Channel MOSFET High-Side Switch Not Fully Turning Off (ESP32 rail at 2.9V)

dougw — Wed, 18 Feb 2026 06:28:07 GMT

It sounds like the FET is damaged.

RE: E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

robogary — Tue, 27 Jan 2026 13:56:13 GMT

No design change, the Scrambler is a different robot.

E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

robogary — Tue, 27 Jan 2026 03:08:15 GMT

The RC Hammering Rubber Duck in the Tub has been officially entered into the Fun & Games competition.

I wanted to share some final comments about our robotics club program, Ducks with Hammers, for the Mysticon SciFi convention in western Virginia this past weekend.

Attendance was a little lighter than normal with a major winter storm hitting the eastern US. Another collegue who drove in from Illinois is still in Virginia waiting for roads to be cleared.

One colleague, who was driving from Florida to Virginia, turned around and headed for home with his Ducks with Hammers after hearing the weather forecast. We missed battling those Ducks.
The convention's guest of honor was Gigi Edgley, best known for her portrayal of Chiana on the science fiction series Farscape. She stopped in to say hi to us during our program and check out our robots and projects. She is a really nice lady.

The RC robots are usually the big hit. The RC Hammering Rubber Duck was no exception. A close second was this robot I built in about 30 minutes. Nicknamed the Scrambler, it had a plywood base cut from scrap, with a roller underneath the rear, 2 continuous servos hot glued to the base, interfaced to a radio controller transmitter & receiver. A 100 rpm gearmotor ran continuously coupled to an old mixer beater.
For next year's convention , we're thinking to focus more on building a fleet of combat robots from kitchen utensils and maybe one autonomous project each.

RE: E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

arvindsa — Tue, 27 Jan 2026 03:53:47 GMT

Ah, i see, your previous video the duck was yellow and a prominent size in comparison with the whole body of robot. I guess i missed an update of your design change.

RE: E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

robogary — Tue, 27 Jan 2026 03:39:41 GMT

Everyone is entitled to an opinion, but my vote overwhelmingly goes to Gigi.

The Scrambler robot doesn't have eyes, it has small rubber ducks mounted on the front.

RE: E14 Fun & Games - Epilogue for the RC Hammering Rubber Duck in the Tub

arvindsa — Tue, 27 Jan 2026 03:18:12 GMT

The robot is more eye catching than Gigi. I do wish you'd not give him eyes each looking outward

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

arvindsa — Mon, 19 Jan 2026 06:52:04 GMT

My take:
Pros of Arduino / Cons of STM32HAL

Easily understandable and tweak-able to most of the maker community, Openness.
Easier to interface with ESP32 (if i am using with ARduino), One IDE for both
Libraries are all available, stable and debugging if any can be done by the God command - serial.print
I dont have to regenerate config in STM32 if i have to
Faster development
If the judge doesn't know STM32, i don't know how it will affect the evaluation

Cons of Arduino/Pros of STM32HAL

Seriously efficient processing, overhead of arduino is lost
I can pull maximum juice of the battery by making it power efficient.;
I can stroke my ego saying i did my hobby project in STM32HAL and refer to Phil's Lab youtube video. I love that guy
In a custom PCB with HSE and LSE etc, Arduino can fail sometimes. Debugging is hard. Also, i can use the Chip & Oscillators i have on hand. Just change the config. I can do this in arduino also, but again, sometimes you will run into problems, and i have to generate the clock configuration for arduino code anyway

Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

arvindsa — Thu, 15 Jan 2026 14:32:48 GMT

The PCB has been delivered. I got some parts enroute and in that time ive got to thinking. Should I code in Arduino or Should I do in stm32HAL? I have my pros and cons listed. For now my only strong reason to stick to Arduino would be because I intend to make this open source and want others to tinker with it

If you were developing this, why would you choose stm32hal ?

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

michaelkellett — Fri, 16 Jan 2026 12:21:39 GMT

The best coding environment depends a lot on the project, its planned life time and, of course, the experience and goals of the developer.

It would be good if you posted your pros and cons as well as describing the project a bit more - otherwise you'll get only very general advice.

As I expect you know the STM HAL can be used in many different development environments and with different operating systems - if you need precise control over the processor resources and hardware then it will be your best bet.

The Arduino environment is more accessible to a large number of hobby type developers and supports wide range of hardware - it works at a much more abstracted level than the STM HAL which may (or may not) appeal for this project.

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

dougw — Fri, 16 Jan 2026 00:52:18 GMT

Unless you have some higher priority, go with what ever gets the job done the quickest. If you do have some higher priority, this question wouldn't be needed...☺

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

Jan Cumps — Thu, 15 Jan 2026 22:03:49 GMT

I've done it for an eLoad's firmware: it was complete on FreeRTOS on a TI Hercules controller. Ported it to TI-RTOS on an MSP432.

The RTOS move was fairly straightforward. FreeRTOS and TI-RTOS aren't the same, but have the same mechanisms (scheduling, messaging, semaphores ...).
The most work went into the peripherals (UART, I2C, SPI) - and interrupt controlled logic. Porting from one controller's HAL to the other, was the biggest task.

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

robogary — Thu, 15 Jan 2026 19:23:54 GMT

Your suggestion made me chuckle. Some of my projects have gotten so old I have to upgrade them to maintain them :-) 😀

RE: Question: Connect4 On the Go v2: Should I code in Arduino or STM32HAL

beacon_dave — Thu, 15 Jan 2026 18:46:16 GMT

I might have to suggest it as a new Project14 theme. 🙂

"revisit an old project and transition it to a new ecosystem..."