ESPRoomba

Inspired by cybrox's implementation using ESP32 as a Roomba controller. Instead of using ESP32 as a dedicated webserver, the ESP32 is made into a CoAP server that any CoAP client can subscribe to (one possibility is to use a nodeJS server as a CoAP client).

Hardware

1. ESP32 DevKitC
2. Switching (step-down) Regulator
3. Bi-Directional Level Converterr
4. Terminal blocks
5. Switch

Circuit Connections

• The Pololu step-down regulator has 5 pins. For this exercise, only 3 pins were used. IN is connected to the unregulated battery of the robot, GND is connected to the GND of the robot and OUT is connected to DevKitC's 5V pin.
• Instead of using a 3.3V step-down regulator, a 5V version is used instead. This is to allow the level converter to use the same 5V input to the DevKitC as reference voltage (high side).
• A simple voltage divider can also be used to bring down the UART RX to less than 5V (ESP32 is not 5V tolerant) but a level converter is used instead.
• IO16 and IO17 are used as UART RX and TX respectively. IO18 is used to pulse the BRC pin low (not fully tested if working).
• IO16 is connected to Roomba TXD pin (through level converter) and IO17 to Roomba RXD.
• The 5V and 3.3V pins are used as reference voltages for the high and low sides of the level converter.

CoAP Endpoints

1. /sc -> for simple commands
   • /sc?mode=start -> put into passive mode
   • /sc?mode=safe -> safe mode
   • /sc?mode=full -> full mode
   • /sc?clean=clean -> send clean opcode
   • /sc?clean=max -> send max opcode
   • /sc?clean=dock -> send seek and dock opcode
   • /sc?clean=spot -> send spot opcode
2. /sked -> send schedule to Roomba
   • use payload option here in JSON format; days are three letter words (mon, tue, wed, thu, fri, sat, sun), hour under hr key and minute in mn key

   {
      mon: {
        hr: 12,
        mn: 45
      },
      fri: {
        hr: 13,
        mn: 00
      }
    }
   

3. /obs -> subscribe to Roomba sensors, data is sent every 15ms.
4. /drive -> to drive left and right wheels using PWM which are sent as payload with the format ${int leftSpeed},${int rightSpeed}

To Do's

• Make commands handling simpler
• Add actuator handlers
• Add simple circuit diagram for connections
• Implement multicast for CoAP (?)