Does anyone got WROOM antenna radiation pattern graph?
Which way does it radiate most?

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Maybe a joule thief
You can use your 0.2Ah battery. Value 0.2A (and even more) I wrote before is true when everything is on. Just remember about it writing a code, switch into powersave mode as often as it is possible, use pullups 10k and do not use a wifi too often

Each time, when I2C's lines SCL or SDL stops connect (eg. I am unplugging it), i2c_master_cmd_begin returns ESP_FAIL or ESP_ERR_TIMEOUT . If ESP_ERR_TIMEOUT is returned, I2C wont work anymore - after replugging disconnected pins, result is still ESP_ERR_TIMEOUT . How to protect it to recover after d...

5V power supply would damage esp.
Esp if you're not too frugal (wifi on, low value resistors for pullups) needs about 0.2A and your battery will die in 1 hour.

CPU freq is 240MHz. Timer configuration is like the one below. I check if timer_val (from timer_get_counter_value) is larger than 36621 (36621 * 0xffff = 2 399 957 235). I believed it was 10seconds, but it seems to take more than 31 secs; why? Are some timers used by WiFi or interface's (I2C, SPI, S...

I would use WROOM module, so VDD3P3_RTC is not available.
How can I hold RTC when main power is down and do not drain its energy too fast - how to programmatically switch off everything but RTC, what current is needed than?

I use esp-wroom-32 module (so flash is build in). I need sd card interface and two more independent SPI interfaces.
I see SPICLK - SCK/CLK, HSPICLK - IO14, VSPICLK - IO18. Where is last, fourth one clk pin?
What about its speed? Which is best for TFT Display connection?

How to use gpio_cd and gpio_wp?
I am unable to find it anywhere else but inside sdmmc_host_init_slot.

Working with WiFi, whenever I alloc any buffer larger than ~64bytes, my code crashes, but whats important I am unable to detect any accurate place where it does. Like there would be no more memory and when some background things for WiFi receive some packets, alloc space for them, the code stops: ch...