ESP32 bear minimum hardware design

[Ifthekhar]

Hello,
I want to design an ESP32-based BLE UART circuit just like the HC-05 module. I have a confusion regarding the hardware and software parts.

Each esp32 module has an external flash memory chip. Is it possible to program the barebone ESP32 IC without the external flash memory chip using Arduino IDE for my specific purpose? I just want to use the BLE UART function with a few GPIO pins.

Thank you.

[ESP_Sprite]

No. The external flash (aside from some eFuses) is the only thing programmable on a 'bare' ESP32 chip. However, you can get ESP32 packages where the 'external' flash is in the same QFN chip case as the ESP32 die; it looks like an ESP32 but has 'internal' flash (which you use in the same way as 'external' flash).

[Ifthekhar]

Thank you. Is it the "Pico D4" version of the MCU? Please correct me if I'm wrong, so in a way,

1. if I just connect power and an antenna I should be able to use it as a stand-alone MCU?

2. And In the case of programming the board I'll just use an FTDI board and to enable the programming mode I'll just use a couple of switches with a pull-up resistor with the reset and prog pins?

3. Will I be able to program the MCU using Arduino IDE?

[ESP_Sprite]

The Pico-D4 is one of the choices (although nowadays it's preferable to go with the esp32-pico-v3 as it has newer silicon) that will probably work well for you as it requires the least amount of components externally. Figure 4 of its datasheet has an implementation diagram. Note that RF antennas are a bit of dark voodoo magic, hence the TBD values for the L and the C; ideally you'd need a vector network analyzer to determine those, but you could look up values that other schematics use and use them for an one-off. It's always a good idea to browse through the hardware design guidelines, but you do need to keep in mind the Pico already integrates a lot of the components mentioned there so a fair bit of the items in it you don't need to worry about.

[Ifthekhar]

Again thanks. as you mentioned the pico should have a lot of components already integrated but I could not locate a circuit diagram with esp32-pico-v3 or pico D4. Maybe I am looking into the wrong repository. Would it be possible to direct me to the resource page of espressif where I'll be able to find the circuit diagram based on pico (without external flash and bare minimum components)?

Also, will I be able to program the pico with an FTDI board, and without the external flash will I be able to program it using Arduino IDE?

I also have noticed another (maybe new) version of ESP, its ESP32-C3. please correct me if I'm wrong, it also seems to have the built-in flash. I am sorry to sound like a broken record but will I be able to program it with FTDI board using the Arduino IDE without the external flash?

[savage]

There are some schematics in the datasheet. See chapters 5 and 6.

[ESP_Sprite]

If the C3 has enough features for you (because, do note, it is a different chip than the original ESP32), you can certainly use that. You wouldn't even need the FTDI board as it has an internal USB-serial-JTAG converter: just connect an USB cable and you're good to go.