I don't see rtc_gpio_init in your loop

SDIO slave means ESP32 is connected to another processor and acts as a slave instead of using flash.

No most peripherals require the main CPU and clock to be powered up and the ulp cannot access that memory space. But if you have a 32khz crystal you may be able to use it as a secondary reference

Do you set host.flags = SDMMC_HOST_FLAG_1BIT and slot_config.width = 1 ?

https://esp32.com/viewtopic.php?f=17&t=4666

It would be easier to hold the esp32 on the programmer board in reset and connect the USB uart pins to the target board but maybe you had a reason not to do that

Are you talking about the Arduino version? If so you should post in Arduino forum.

Vader_Mester wrote: I'm also sure they have the certifications as well, so contacting them would help you.

I don't think so, what is the ID?

Yes you should always specify which code base

https://github.com/espressif/arduino-esp32/issues/1145

Yes it seems like an oversight because it's just a matter of paperwork to file for IC using fcc test results so I suggest you push your sales rep to get it resolved based on your EAU.

Also there are cs setup time configuration registers.

Well this is not an m5stack forum so one thread would be nice unless you have a generic problem. But you can make as many threads on http://forum.m5stack.com and their GitHub repos as you want.