ESP8266 NodeMCU for MIT Scratch 2
The aim of this project is giving microcontroller control into hand of kids. Scratch or Roboremo can be used as user interface. ESP8266 is a cheap microcontroller with built-in WiFi (SoC). See IoT for $10 for a "Hello, World!" example. There are a lot of variants, examples are optimized for WeMos D1 mini.
Components:
- ESP8266: microcontroller with built-in WiFi (required)
- NodeMCU firmware (required)
- Controller, written in Lua for executing control commands and providing sensor values (required)
- H-bridge (optional)
- HC-SR04 (optional)
- Scratch 2 Offline Editor: a programming interface (optional)
- Bridge, a Scratch Extension written in Python (required to Scratch)
- Python interpreter (required to Scratch)
- Roboremo: a simple manual control interface on Android (optional)
Example setups:
+----------+
+--------------+ +-->| HC-SR04 |
| +--+ +----------+
+--->| Controller |
+-----------+ +----------+ | | +--+ +----------+
| | HTTP | +---+ +--------------+ +-->| H-bridge |
| Scratch +------->| Bridge | WiFi +----------+
| | | +---+ +--------------+
+-----------+ +----------+ | | | +----------+
+--->| Controller +----->| H-bridge |
| | +----------+
+--------------+
+----------+
+------------+ +--------------+ +-->| H-bridge |
| | WiFi | +--+ +----------+
| RoboRemo +------->| Controller |
| | | +--+ +----------+
+------------+ +------+-------+ +-->| HC-SR04 |
| +----------+
WiFi |
V
+--------------+
| | +----------+
| Controller +----->| H-bridge |
| | +----------+
+--------------+
Supported Scratch commands:
- initNet: Initialize WiFi subnet (only one subnet is supported simultaneously), IP address is a sum of subnet address and device id.
- pinMode: NodeMCU command(s): gpio.mode or pwm.setup + pwm.start
- digitalWrite: NodeMCU command(s): gpio.write
- analogWrite: NodeMCU command(s): pwm.setduty
- analogPairWrite: NodeMCU command(s): pwm.setduty
- tankWrite: NodeMCU command(s): pwm.setduty
- servoWrite: NodeMCU command(s): gpio.write
- digitalRead: NodeMCU command(s): gpio.read
- analogRead: NodeMCU command(s): adc.read or custom sensor command
- reset_all: Reset state machine, NodeMCU command(s): gpio.write, pwm.setduty
- poll:
Bridge Features:
- Supporting more NodeMCUs in one WiFi network
- Command-line parameters
- Overload protection by state machine (only changes are sent to Controller)
- Overload protection by UDP "ACK"
- Overload protection by batch command sending
- Overload protection by rare poll and caching digitalRead/analogRead values
- Overload protection by queue size limitation (drop)
- Unit tests
Controller Features:
- analogPairWrite: transform a [-100,+100] value to 2 pins of H-bridge for a DC motor
- tankWrite: transform a ([-100,+100], [-100,+100]) value pair to pins of H-bridge for 2 DC motor
- UDP
- TCP
- Supporting more NodeMCUs in one WiFi network, for Bridge
- Supporting more NodeMCUs in one WiFi network, for Roboremo (proxy)
- HC-SR04 sensor support
- DHT sensor support
- BMP180 sensor support
WeMos D1 mini system has some additional resistors and dedicated pins for shields. These constraints determine a logical pinout:
| ESP-8266 Pin | Pin | WeMos Function | ESP4S2 Function |
|---|---|---|---|
| A0 | A0 | Analog input, max 3.3V input | Analog input |
| GPIO16 | D0 | IO | HC-SR04 Trig |
| GPIO5 | D1 | IO, SCL | I2C for shields |
| GPIO4 | D2 | IO, SDA | I2C for shields |
| GPIO0 | D3 | IO, 10k Pull-up | H-bridge B2 |
| GPIO2 | D4 | IO, BUILTIN_LED 10k Pull-up |
Blue LED DHT Data |
| GPIO14 | D5 | IO, SCK | H-bridge A1 |
| GPIO12 | D6 | IO, MISO | H-bridge A2 |
| GPIO13 | D7 | IO, MOSI | H-bridge B1 |
| GPIO15 | D8 | IO, SS 10k Pull-down |
HC-SR04 Echo + 4k7: 5V-->3.3V voltage divider |
D8 pin works well with Pololu DRV8833 as B2 input, but activates motor B with cheap L9110 at power on. D3 works well with cheap L9110. I2C pins are used by shields OLED and Motor.
HC-SR04 needs 5V power and Echo pin output is 5V, too (3.3V input is good for Trig). A 4k7 with 10k Pull-down resistor behave as a voltage divider, see: HC-SR04 Ultrasonic Range Sensor on the Raspberry Pi.
Other pinout can also be used.
NodeMCU is an embedded Lua firmware to ESP8266. Firmware can be download from NodeMCU custom builds (builds combined binary). For using H-bridge, PWM module must be selected. For using DHT sensor, DHT module must be selected. Integer build must be used. Firmware can be flashed by esptool.py or NodeMCU Flasher, see Flashing the firmware. Since 1.5.1-master, default baud switched to 115200.
ESPlorer can be used to upload Lua files to ESP.
Copy secure.lua.example to secure.lua and edit own WiFi authentication configuration.
Copy config.lua.example to config.lua and edit network configuration. Controller supports more WiFi network configuration, selected by WIFI_CFG_NAME. ESP microcontrollers are identified by its MAC address. STATION and AP mode are supported. In STATION mode (wifiMode=wifi.STATION), Controller requests an IP address from a WiFi AP (a WiFi router or an ESP8266 in SOFTAP or STATIONAP mode). If WiFi AP is not alive, ip parameter will be used. If static_ip=true, Controller enforces ip as IP address (netmask should be declared, too). In SOFTAP mode (wifiMode=wifi.SOFTAP), NodeMCU runs as WiFi AP and WiFi router is not required for WiFi communication. Other Controllers in this WiFi network should be configured with static IP address (static_ip=true). Devices with custom feature can be configured in devices.
Upload all *.lua files of directory lua to NodeMCU. After reset, NodeMCU will be ready to receive commands and send back input values.