ESP32 Forum

Hi everyone,
I'm a cs student and I've been assigned a hardware project that involves designing a modular central unit based on the ESP32-PICO-D4. The requirements are:
- Use of 3x ESP32-PICO-D4 processors
- Power module with 5V USB input and battery connection with a charging circuit
- Processor module with ISP and JTAG inputs
- Two buttons: BOOT and RESET
This is how the project looks so far. Are the power and reset circuits correctly implemented? I would really appreciate any advice or suggestions. Thanks

Generally, please follow figure 12 of the datasheet of the Pico SoM (System on Module as in the ESP32-Pico-D4 'chip'). Some differences:

- VDDA_2 is not connected. Suggest you compare Figure 12 and your schematic to make sure all the pins that need to be connected to 3.3V actually are.
- EN needs a RC network, you only have a R. The datasheet doesn't name values, but 10K/1uF tends to work fine for most power supplies.
- No need to connect VDD_SIO to 3V3, I don't think it's even connected within the SoM.
- You probably want to add a 0.1uF capacitor close to the SoM. Maybe this is not 100% necessary, but hey, belts and braces and stuff.
- If your thing is battery-powered, you need to design that bit of the schematic up front. Using an AMS1117 for battery powered operations is possible, but is really not optimal (wrt quiescent current, minimal input voltage etc).
- Maybe it's a good idea to connect EN and IO0 to J1 as well. This allows you to reprogram the module in a hands-off manner using e.g. an ESP-Prog board.

Aside from that, it looks OK, but I suggest you post the schematic after you're done as at the moment we cannot see if connections/components are not there because the schematic is preliminary or because you forgot them.

When creating the boot and reset buttons, I referred to the schematic you sent, but I wasn’t able to find any example of how to connect the battery with the charger. Could you please take a look at my schematic and let me know if it’s correct? I’ll add the JTAG and ISP connections afterwards.

When creating the boot and reset buttons, I referred to the schematic you sent, but I wasn’t able to find any example of how to connect the battery with the charger. Could you please take a look at my schematic and let me know if it’s correct? I’ll add the JTAG and ISP connections afterwards.

At first glance: not sure what D2 is good for, and an 150mA LDO is way too small for an ESP32; I think the datasheet mentions 600mA at least. If you want an indication on how to build it, there are devboards out there (Sparkfun, Lilygo, Waveshare, ...) which can use a LiIon battery as a power source and have schematics released by the manufacturers.

VDDA_3 is also not connected