Don Park

• 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

• switch
• switch backlight
• photosensor
• distance sensor
• status led
• lcd display

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

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