|Model|Core| Co-Proc | Ram|Wifi|Bluetooth|Peripherals|
|ESP32   | Extensa 32bit LX6 240MHz (2) | FSM | 520k | wifi4 | bt4.2 |
|ESP32-S2| Extensa 32bit LX7 240MHz (1) | FSM & RISC-V | 320k | wifi4 | x | USB Serial, 8-bit DAC(2) |
|ESP32-S3| Extensa 32bit LX7 240MHz (2) | FSM & RISC-V | 512k | wifi4 | ble5 | USB Serial |
|ESP32-C2| RISC-V 32bit 120MHz (1) | | 272k | wifi4 | ble5 |
|ESP32-C3| RISC-V 32bit 160MHz (1) | | 384k | wifi4 | ble5 |
|ESP32-C6| RISC-V 32bit 160MHz (1) | | 384k | wifi6(2.4ghz) | ble5 + zigbee |
|ESP32-H2| RISC-V 32bit  96MHz (1) | | 256k | x | ble5 + zigbee |


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### Blinky (ESP32-S module; ESP32 + 4m flash)

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  * ESP-Strapping
    * GPIO
      * GPIO12 float low - low 3.3v, high 1.8v (VDD_SDIO)

      * GPIO15 float high U0TXD - high logging, low silent 

      * GPIO 0 float high, GPIO 2 float low - Flash boot
      * GPIO 0 gnd low, GPIO 2 float low - Serial boot
    * ESP32-S pins
      * pin25 - programming
      * 1,38,15 - GNDs
      * 2 - pwr, 3 - enable
      * ADC1 (ADC2 unavailable w/ wifi)
  * Sep 2019
    * oshpark https://oshpark.com/shared_projects/1DoMmw6E

  * Oct 2019
    * Move ADC port to an ADC1 Pin pin4-9
    * Another ADC Pin to 3.3v input?
    * Another ADC Pin to vdivider + 15v input
    * Add 3.3v to top of ADC
    * drop 3.3io and 3.3 power ports
    * add oled/serial port at edge
    * short rx/tx lines pin34&pin35

  * Nov-B 2019 (send to pcbs.io)
    * LMS8117AMP-3.3/NOPB
    * LCD pin23 DO, pin16 CLK. (any GPIO)
    * POWER idle 115mA with esphome
    * POWER 16 neopix 17ma(low) 177ma (full red or green or blue) 305ma full white 
    * POWER neopix 20ma per color per led

  * Nov-C 2019
    * Reset line (no room)
    * connected 3v bus
    * vreg cap
    * volt Divider ADC (no room)
    * add pullup resistor to one port (for i2c temp sensor)
    * U0 TX 500ohm R close to esp32 (reflections)

  * Dec-D 2019
    * move pin20 (SD1 CLK) to 12 G27 DONE
    * add 4-pin switch port (switch+status led)
    * LVDS connector
    * GPIO12 1.8 vs 3.3v pin14
    * flip micro USB DONE

## wall switch
  * switch
  * switch backlight
  * photosensor
  * distance sensor
  * status led
  * lcd display

## photoresistor
  * super-bright (from cell phone) 300KOhm
  * super-dark (fabric lightly covered) 10MOhm

## signal harmonics
https://electronics.stackexchange.com/questions/33372/spi-bus-termination-considerations