ESP32-TERM

Features

• ESP32 Module
  • 18 Analog-to-Digital Converter (ADC) channels
  • 10 Capacitive sensing GPIOs
  • 3 UART interfaces
  • 3 SPI interfaces
  • 2 I2C interfaces
  • 16 PWM output channels
  • 2 Digital-to-Analog Converters (DAC)
  • 2 I2S interfaces
• 6-bit VGA color
  • 2:2:2 R:G:B
• PS-2 DIN keyboard connector
  • 5V keyboard
  • 3.3V to 5V level shifters
    • Better than 5V keyboard with series resistors
  • 10K pull-ups on both sides
• FTDI connectors
• LED on P27
• 5V DC on USB-B
• 95x95mm ODAS form factor
• 6-32 mounting holes

ESP-32 Module

• Uses the ESP32 DevKit ESP32-WROOM GPIO Pinout
• On board Blue LED = Arduino Pin 2
• There are various modules out there with different pinouts, but this card uses this one

ESP-32 Module Pinout

"Chip" on the module

ESP32 Pin Usage - Revs 2, 3

Module Features

• Architecture: Xtensa Dual-Core 32-bit LX6
• CPU frequency: up to 240MHz
• Total RAM available: 528KB (part of it reserved for system)
• BootROM: 448KB
• Internal FlashROM: none
• External FlashROM: code and data, via SPI Flash; usual size 4MB
• GPIO: 34 (GPIOs are multiplexed with other functions, including external FlashROM, UART, etc.)
• UART: 3 RX/TX UART (no hardware handshaking), one TX-only UART
• SPI: 4 SPI interfaces (one used for FlashROM)
• I2C: 2 I2C (bitbang implementation available on any pins)
• I2S: 2
• ADC: 12-bit SAR ADC up to 18 channels
• DAC: 2 8-bit DACs
• RMT: 8 channels allowing accurate pulse transmit/receive
• Programming: using BootROM bootloader from UART - due to external FlashROM and always-available BootROM bootloader, the ESP32 is not brickable

Video DAC LTSpice Simulation

• Video DAC Simulation files
• Video is 2:2:2 - R:G:B

Summing Video Resistor DAC

• Best values (1%)
  • 422, 845
  • 470, 820 are close/standard values
• 0.7V into 75 Ohm VGA load
• 3.3V drive
• ESP32 has 40 mA drive
  • Uses 8 mA (max)
• Output in 4 equal voltage steps

Connectors

P1 - VGA

• DB-15HD connector
• 64-colrs
• ESP32 pins

  HSync => GPIO23
  VSync => GPIO15
  R0    => GPIO22
  R1    => GPIO21
  G0    => GPIO19
  G1    => GPIO18
  B0    => GPIO5
  B1    => GPIO4

VGA - Resistor Selection

• ESP32 has a 3.3V driver which can drive more than 10 mA
• Ideal case drive current
  • 0.7V (full scale VGA level) into 75 Ohms = 9.33 mA
  • 2/3 of the current or 6.16 mA comes from the lower value resistor (digital most significant bit)
  • 1/3 of the current or 3.08 mA comes from the higher value resistor (digital least significant bit)
• R-2R values
  • Ideal resistor values are 417.9 ohms and 835.7 ohms
  • Standard value 1% resistors
  • 1% standard values are 422 (Mouser), 845 (Mouser) Ohms
    • Get closest values
    • 0V, 0.228V, 0.460V, 0.693V
• Voltage steps are:

• Current steps are:

P2 - PS/2 Keyboard

• Purple DIN 6 connector
• ESP32 pins

  KBDAT   => GPIO32
  KBCLK   => GPIO33

P3 - PS/2 mOUSE

• Green DIN 6 connector
• ESP32 pins

  MSEDAT   => GPIO
  MSECLK   => GPIO

P4 - Audio Out

• Wired on both pins of stereo 3.5mm Jack
• ESP32 pins

  AUD   => GPIO25

P5 - RS-232

• DB-9 Female
• DCE wiring

P6 - 5V Power

• USB-B connector
• Power only

J1 - 5V Power Header

• 2z3 right angle header
• Can be used for power in or out of the card
  • Only one power source can be used with the card

J2 - FTDI Power in/out

• Don't install jumper if an external FTDI interface is used
  • Useful to power external DTE or DCE RS-232 card

J3 - FTDI #2

• Most recent (2020-02) ANSI terminal uses pin 34 for Rx
• Pinout

1. GND
2. RTS (Not used)
3. 5V (Power in if J2 is configured
4. RX (to ESP32)
5. TX (from ESP32)
6. CTS (Not used)

  RX2    => GPIO34
  TX2    => GPIO2

Connect to FTDI card

• Set FTDI jumper to 3.3V (image below shows jumper set to 5V which is wrong)

J5 - Serial Source Selection Header

• Select either RS-232 connector or FTDI connector

DCE - RS-232 to TTL

• The DCE (peripheral) has the female DB-9 connector

• The DTE (PC) has the male DB-9 connector

J3 - 5V

• 2x4 5V/GND header

J4 - SD Card

• Brought to SD Card

  MOSI  => GPIO17
  MISO  => GPIO16
  CLK   => GPIO14
  CS    => GPIO13

FabGL GPIOs assignment summary - fabgl dev board rev2

From here

  VGA
    HSync => 23
    VSync => 15
    R0    => 21
    R1    => 22
    G0    => 18
    G1    => 19
    B0    => 4
    B1    => 5

  Audio
    AUD   => 25

  PS/2 - Keyboard
    DAT   => 32
    CLK   => 33

  PS/2 - Mouse (Not used)
    DAT   => 27
    CLK   => 26

  SDCard - HSPI
    MOSI  => 17 (12 on TTGO/WROVER)
    MISO  => 16 (2 on TTGO, 35 WROVER)
    CLK   => 14
    CS    => 13

  UART - UART1 (USB - not used)
    RX    => 3
    TX    => 1

  UART - UART2
    RX    => 34
    TX    => 2  (not usable on TTGO/WROVER with SDCard active)

Software

FabGL Arduino library

Installing the released library

Using Latest FabGL builds

• Fabrizio does a nice job of keeping his Arduino libraries up to date but if you want a bleeding edge experience, you can download his code from GitHub. Note, he's in active development so things often change.

Here's how I did it

1. Install drivers via Arduino from the Library Manager. These are not the latest files. Space Invaders should run but not have sound (as of now because it's the older version).
2. Move the FabGL from the Arduino libraries file folder to the desktop.
3. Copy the FabGL from the GitHub download to the Arduino files folder (where you removed the other folder).
4. Examples will now be the latest.
5. Compile/download/test the new files. You know it works if you now get sound from Space Invaders.
6. Save as where you would normally save your Arduino sketches.

Arduino Programming

• Installing the ESP32 Board in Arduino IDE (Windows, Mac OS X, Linux)
• Board : "DOIT ESP32 DEVKIT V1"
  • Used Board : ESP32 Dev Module with Tools > Partition Scheme > Huge APP option to run VIC-20 (2022-09)
• DOIT module does not have PSRAM
  • Can't run PC Emulator without PSRAM
• If you try to upload a new sketch to your ESP32 and you get this error message “A fatal error occurred: Failed to connect to ESP32: Timed out… Connecting…“. It means that your ESP32 is not in flashing/uploading mode.
• Press the “Upload” button in the Arduino IDE to upload your sketch
• After you see the “Connecting….” message in your Arduino IDE, release the finger from the “BOOT” button:

Other Builds

<video type="youtube">LOhmlOyUw4w/video>

Assembly Sheet

• ESP32-VGA Interactive BOM