The ESP32 Command Station supports many configurations, some of which can be
automatically configured by the menuconfig utility.
The ESP32 Command Station code is able to support almost any model of ESP32 or ESP32-S3, provided there are sufficient GPIO pins available.
The ESPDuino-32 uses an ESP-WROOM-32 SoC in an Arduino UNO form-factor. This is a very easy to use ESP32 board that interfaces very well with the Arduino Motor Shield.
NOTE: There have been reports that this board may not always enter download mode. If the board does not enter download mode automatically connect a jumper wire from IO0 (pin closest to barrel jack) to GND (second and third pin from right in the same pin header) for downloading firmware and remove for normal operations.
When pairing this with the Arduino Motor Shield or compatible L298 modules, please refer to Arduino Motor Shield Required Jumpers for details on required jumpers.
The Espressif ESP32 DevKit-C boards are a great option but require many jumper wires to connect the ESP32 with the h-bridge(s) or other peripherals.
The LilyGo TTGO-T1 board is an inexpensive board that has a built-in MicroSD card adapter. This is a great alternative to the ESPDuino-32 board when not using an Arduino Motor Shield. Similar to the Espressif ESP32 DevKit-C this board will require many jumper wires to interface with various h-bridge(s).
ESP32 Command Station supports multiple h-bridge chips, many of which are available in a shield or carrier board design.
The Arduino Motor Shield is built around the L298 h-bridge chip which has two outputs (A and B), each supporting up to 2 Amps (some modifications required).
The official shield can be purchased here,
there are also a number of compatible clones such as the one below:
NOTE: The above image has an optional heatsink attached to the L298P IC.
NOTE: When this shield is paired with the ESPDuino-32, IO0 is the unmarked pin to the left of IOREF.
Using this motor shield with ESP32 Command Station will require at least one jumper:
| Pin 1 | Pin 2 | Notes |
|---|---|---|
| 12 / DIRA (ESP32: 19) | 13 / DIRB (ESP32: 18) | This is necessary as the ESP32 Command Station generates the DCC signal on ONE GPIO pin. |
| A0 (ESP32: 2) | A2 (ESP32: 35) | Required when using with ESPDuino-32. |
| A1 (ESP32: 4) | A3 (ESP32: 34) | Required when using with ESPDuino-32. |
There are a number of red PCBs with an L298 mounted vertically that are similar to this one:
The are generally based on the same L298 chip that is used for the Arduino Motor Shield but a few use the L293 IC and is advertised as a stepper motor driver.
These require modifications and extra components to be usable, specifically:
- Current sense is NOT routed to any external pins!
- IN1 and IN2 must be the inverse of eachother, similarly for IN3 and IN4.
For IN1, IN2, IN3, IN4 a circuit similar to this can be used:
Alternatively a 74HC08 IC can be used to invert the signal.
The LMD18200T provides up to 3 Amps for ONE track output. This h-bridge requires only four connections to the ESP32:
- GND
- PWM (enable pin)
- DIR (DCC signal pin)
- BRAKE
Unfortunately most PCBs do not expose the current sense pin (8) and connect this directly to GND or not connected at all!
The DRV8873 can provide 5-10 Amps for ONE track output. This h-bridge is suitable for RailCom cut-out generation.
This h-bridge is not available in a commercial breakout board at this time.
The DRV8800 / DRV8801 can provide up to 2.8 Amps for ONE track output. This h-bridge is suitable for RailCom cut-out generation.
Pololu offers the DRV8801 as a breakout board and can be used with the following connections:
- VDD to 3v3.
- DIR to DCC signal pin.
- PWM to track enable pin.
- VMM to track power supply (minimum 12v DC)
- OUT - and OUT + to track.
- BRK to track brake pin, if RailCom cut-out is enabled otherwise no connection.
The MC33926 based shield and carriers from Pololu can provide up to 2.5 Amps on TWO track outputs.
This is not a recommended h-bridge as there are built-in circuit breakers which can trip when a short occurs and the ESP32 will not know.
The BTS7960B (usually referred to as IBT_2) can provide up to 43 Amps for ONE track output.
This is not a recommended h-bridge due to the high amperage rating and no reliable/accurate way to limit the current to lower levels.
The ESP32 Command Station supports connecting an I2C based display which is used to display real-time data from the running system.
The SH1106 or SSD1306 OLED displays are fairly inexpensive and come in a variety of shapes and sizes. The preferred size is 128x64 pixels.
There are many options available with two or four lines with either sixteen or twenty columns. The preferred size is twenty columns and four lines.
An external CAN transceiver is required for utilizing the OpenLCB (LCC) CAN based connections between the ESP32 Command Station and other OpenLCB (LCC) nodes.
At this time the following external CAN transceivers have been tested and confirmed as working:
- TJA1057/3 -- split voltage CAN transceiver from NXP Semiconductors.
- IFX1050GVIOXUMA1 -- split voltage CAN transceiver from Infineon.
- MCP2551 -- CAN transceiver from Microchip Technology.
- SN65HVD23x -- CAN transceiver from Texas Instruments.
The split voltage CAN transceivers are preferred as the logic IO (RX and TX) can use 3v3 logic which is compatible with the ESP32/ESP32-S3 GPIO pins.
NOTE: MCP2551 has been tested ONLY using 5v as VDD with 3v3 logic on the CAN TX pin and a voltage divider on the CAN RX pin to reduce the maximum voltage to 3v3 to protect the ESP32/ESP32-S3 GPIO pins from the 5v logic level used by the MCP2551.