The joint download boot mode on the ESP32-C6 supports firmware download via SDIO. How can this mode be used? for example when connected to a P4, is there a special firmware that can be loaded onto the P4 that will forward the firmware to the C6 through SDIO?

The hardware design guidelines for the ESP32-S2 recommend:

If an oscillator is used, its output should be connected to XTAL_P on the chip through a DC blocking capacitor
(about 50 pF). XTAL_N can be floating. Please make sure that the oscillator output is stable and its accuracy is
within ±10 ppm ...

the hardware design guidelines https://docs.espressif.com/projects/esp-hardware-design-guidelines/en/latest/esp32p4/schematic-checklist-esp32p4.html show two different reference schematics for chip revisions >=3.0 and for chip revisions <3.0

If I'm not mistaken the only differences are

1. pre 3.0 ...

The esp_hosted repository https://github.com/espressif/esp-hosted-mcu contains the folder 'slave' which contains the firmware code to run on the wifi-enabled esp32 soc. It has its own readme which instructs to use it like an example, so it can be copied into a new project by calling

idf.py create ...

I'm using visual studio code with the ESP-IDF extension. I've already done a fresh install and am still getting the same error:

>idf.py create-project-from-example "espressif/esp_hosted:slave"
Executing action: create-project-from-example
Traceback (most recent call last):
File "C:\esp\v6.0\esp ...

The ESP-IDF documentation for the SPI slave driver on the P4 (https://docs.espressif.com/projects/esp-idf/en/stable/esp32p4/api-reference/peripherals/spi_slave.html) states:

When an SPI Host is set to 80 MHz or lower frequencies, routing SPI pins via GPIO matrix will behave the same compared to ...

So currently the esp32-c6, c61 and c5 only have an SDIO slave driver, the P4 only has an SDIO host driver and the classical esp32 has both.

I'd like to know whether this is only a software side omission and in particular whether SDIO slave support would be possible on the P4 or whether the ...

thanks - even if I place the wire away from the antenna in the opposite direction wifi isn't connecting (the crystal XTAL-P pin is also unshielded and if I move the cable away that pin is the closest thing to the antenna). I also notice the esp32-c3 IC getting pretty hot

On the esp32-s3 I can route the 40Mhz clock to a pin with the following code:

#include "driver/gpio.h"
#include "driver/ledc.h"
#include "hal/clk_tree_hal.h"
#include "soc/clkout_channel.h"
#include "soc/io_mux_reg.h"

void route_40mhz_xtal_to_gpio39_s3() {
// 1. Set GPIO 39 as an output
gpio ...

So from some posts I gathered that it should be possible to replace the crystal with a crystal oscillator or other clock source by connecting tge clock output directly to XTAL_P and letting XTAL_N floating.

I tried this here with an esp32-c3 supermini. I removed the crystal and then output CLKOUT ...