Help to build a minimal EPS32 PCB

WoolySheep
Posts: 11
Joined: Wed Jan 06, 2021 9:46 am

Help to build a minimal EPS32 PCB

Postby WoolySheep » Sat Jan 22, 2022 9:10 pm

Hi all,
I have bought a load of the 'ESP32 Dev KitC-V4-32D' and I love them. I am mainly using them to create dataloggers. I want now though to make my own PCBs and put the ESP direct onto it rather than have to solder on the Dev Kit (which costs more money and is a lot larger).

I have taken a look at the official schematic and have come up with what I think is the most minimal layout that would make it run. The idea is that it will be powered from a mobile phone charger and USB cable. As and when I want to program the ESP32, I will plug in a USB TTL device to a 6-pin female header that is on my PCB.

Can people please take a look at my attached design and tell me if this should work, or if I am missing anything or if any of the part values are wrong.

Thank you so much to those who do give me feedback.
Alan
Attachments
1-Schematic.png
1-Schematic.png (156.85 KiB) Viewed 2343 times

ESP_Sprite
Posts: 6346
Joined: Thu Nov 26, 2015 4:08 am

Re: Help to build a minimal EPS32 PCB

Postby ESP_Sprite » Sun Jan 23, 2022 1:57 am

C7 and C3 are in parallel with eachother, so you can remove one of them. Suggest to make whichever one remains 1uF instead as is advised in the datasheet. Also, in my experience, if you don't use the exact transistor as on the devkit and you have issues with the auto-reset circuit, it can help to make R4/R5 4.7K instead. Also note that newer WROOM versions have pin 17 to 22 N/C (and in general, as they clash with the internal flash they're not that useful) so you may want to decide not to bother having connections to them.

(Also also, if you only use them for sensors and program them in ESP-IDF, can I suggest the ESP32C3? The modules are smaller, and as it has a built-in USB-serial converter, you don't need the auto-reset circuit or the external USB-serial converter.)

WoolySheep
Posts: 11
Joined: Wed Jan 06, 2021 9:46 am

Re: Help to build a minimal EPS32 PCB

Postby WoolySheep » Sun Jan 23, 2022 11:42 am

ESP_Sprite wrote:
Sun Jan 23, 2022 1:57 am
C7 and C3 are in parallel with eachother, so you can remove one of them. Suggest to make whichever one remains 1uF instead as is advised in the datasheet. Also, in my experience, if you don't use the exact transistor as on the devkit and you have issues with the auto-reset circuit, it can help to make R4/R5 4.7K instead. Also note that newer WROOM versions have pin 17 to 22 N/C (and in general, as they clash with the internal flash they're not that useful) so you may want to decide not to bother having connections to them.

(Also also, if you only use them for sensors and program them in ESP-IDF, can I suggest the ESP32C3? The modules are smaller, and as it has a built-in USB-serial converter, you don't need the auto-reset circuit or the external USB-serial converter.)


Thank you so much ESP_Sprite, you have helped me out a lot. Please see the attached revised version. How does it look now?
1-Schematic.png
1-Schematic.png (157.92 KiB) Viewed 2280 times


I took a look at the ESP32C3. I think this is something I need to investigate more for sure!


Could I ask you a three more questions please (I am still learning).

1. I don't really need the Switch that brings 'IO0' to ground do I as the DTR/RTS from the USB TTL will automatically reboot the device and put it in programming mode?

2. Thinking of the absolute minimum components, if I removed the two transistors & R4/R5, I could also remove the DTR & RTS connectors to the USB TTL (so I would only need 3v3, GND, TX & RX). Then I would just need to hold down the switch that brings IO0 to ground, then press the reboot switch, yes? That way I would be manually rebooting and putting it into programming mode. This would reduce the components down to the absolute minimum wouldn't it? Would the below work?
1-Schematic Minimal.png
1-Schematic Minimal.png (145.41 KiB) Viewed 2280 times


3. On the underside of the ESP32 is pin 39 which states it is GND. I take it this does need to go to ground? Can I just put a pad under it that goes to ground, or does it actually need soldering? I ask as I will be installing it with a soldering iron, not a Rework Station. If it does, I may put in 2-3 small holes below it, so I can put solder on the pad through the holes (if that makes sense).

Again, thank you for your help with this, I really do appreciate it.
Alan

WoolySheep
Posts: 11
Joined: Wed Jan 06, 2021 9:46 am

Re: Help to build a minimal EPS32 PCB

Postby WoolySheep » Mon Jan 24, 2022 5:20 pm

Hi ESP_Sprite,
Do you think my two schematics are ok?

I know it is the Chinese New Year, but desperate to get a test mock-up PCB designed so I can test out my designs.

Many thanks
Alan

ESP_Sprite
Posts: 6346
Joined: Thu Nov 26, 2015 4:08 am

Re: Help to build a minimal EPS32 PCB

Postby ESP_Sprite » Tue Jan 25, 2022 1:15 am

That should work. One thing you could do is also add the EN and IO0 pins to the programming connector so you could, if you wanted, add the auto-reset circuit externally if you ever get sick of pressing buttons.

WoolySheep
Posts: 11
Joined: Wed Jan 06, 2021 9:46 am

Re: Help to build a minimal EPS32 PCB

Postby WoolySheep » Tue Jan 25, 2022 7:03 am

Hi ESP_Sprite,
Again, thank you for your help. I really like the idea of off-site buttons, I never even through of that. I think it will be best to keep the Reboot button on the board as I can see times it won't be as simple to power cycle the device, but having the Flash/Program button off-site on the USB FTDI would work very well.

Right, time to start designing a test PCB to check both of my designs for real & then order a few ESP devices.

So exciting.
Alan

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