Presentation on GeekCamp.SG 2015

1. Build WiFi Gadgets
using ESP8266
GeekCamp.SG 2015
Zhu Baoshi @ba0sh1

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Internet of Things (?)
• Let coffee pot twitter you a message is less
productive than just a beep!
• Same for turning on/off a light.
• Beware of the over hype!
• But why connect things onto internet?
Remote convenience
Did you forget to … ?
Monitoring
Diagnose / support
Why-not ?
Data driven actuators
Weather

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ESP8266 in IoT Device

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ESP8266 In-a-nutshell
• Developed by Espressif System
• LOW COST
• A 32-bit Microcontroller, using
Tensilica Xtensa core
• RF frontend
• Runs at 80MHz or 160MHz
• External Flash
• ~80kB DRAM
• ~35kB IRAM
• ADC, GPIO, SPI, I2S, DMA
• Part number is ESP8266EX
• 20 million chip sold. 5000 active
developers

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Modules
ESP8266
Flash
26MHz
Crystal
Chip Antenna
or equivalent

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Dev Boards
Adafruit Huzzah Sparkfun
MOD-WIFI-ESP8266-DEV
NodeMCU v1
Mine :D
$9.95 €5.50 $8.5

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Beware of “unauthorized” NodeMCU v1

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Architect ESP8266 project
ESP8266 Arduino /
other MCU
Sensors /
Indicators /
Actuators
The “original” pre-oct-2014 way
Hayes AT alike
instructions

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Dawn of ESP8266 SDK
ESP8266
Sensors /
Indicators /
Actuators
I/O
Expander

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Demo

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Know your Hardware
• WiFi
– Supports 802.11b/g/n, WPA/WPA2
– AP, STA, AP+STA modes
– With my ASUS router it connects at 65Mbps
– With WebSocket speed test I receive 5-6KB/s
– NetIO test best at 1040KB/s, reference from
http://www.esp8266.com/viewtopic.php?f=5&t=2
45 (doing nothing but receive TCP packets)

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Power Power Power!
• ESP8266 is both low power and power hungry
• Test setup:
• Idle mode: 40uA

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Power Consumption @ WiFi idle
100ms
64mA
424mA
847ns
Average for 1 second: 993ms@64mA+7ms@424mA = 66.5mA
With 22uF tantalum bypass capacitor. A bigger capacitor may help reduce the
spike.

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Power Consumption @ WiFi active
Average 67.6mA

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Wakeup-Read-Send-Sleep
Startup
RF
Calibration
Scan AP, Connect,
DHCP
Connect to MQTT,
Publish data
Active for 5.7 seconds: 70.2mA

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Will you go battery power?
Standby Always on
Wake up once
every minute
Wake up once
every hour
2500mAh lithium
battery
7 years 37 hours 15.5 days 689 days
2xAA alkaline
3000mAh
8.4 years 44 hours 18.6 days 827 days
*Your actual millage may vary

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Keep your options open
• Particle Photon ($19)
• Lightblue Bean ($30)
• OpenWRT routers ($7-20)
Linux
USB
High performance
Not low power
Slow boot

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ESP8266 Development H/W
• Module (+ development board)
• USB-Serial adaptor (3.3V)
• A GOOD power supply

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ESP8266 Programming S/W
• ARDUINO IDE
• https://github.com/esp8266/Arduino
(recommend the “Staging” version)
• Compatible with *many* Arduino libraries

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ESP8266 Arduino Library
WiFi.begin(ssid, password);
while (WiFi.status() != WL_CONNECTED) {
delay(500);
Serial.print(".");
}
Serial.println("");
Serial.println("WiFi connected");
Serial.println("IP address: ");
Serial.println(WiFi.localIP());
WiFiClient client;
if (!client.connect(host, httpPort)) {
Serial.println("connection failed");
return;
}
// This will send the request to the server
client.print(String("GET ") + url + " HTTP/1.1rn" + "Host: " + host + "rn" +
"Connection: closernrn");
delay(10);
// Read all the lines of the reply from server and print them to Serial
while(client.available()){
String line = client.readStringUntil('r');
Serial.print(line);
}

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NodeMCU
• http://www.nodemcu.com/index_en.html
(mqtt.lua)
m = mqtt.Client(“client”, 120, “user”, “pass”)
m:connect(“192.168.0.99”, 1831, 0, function(conn)
print("Connected to MQTT:" .. BROKER .. ":" .. BRPORT .." as " .. CLIENTID)
m:publish("sensors/".. CLIENTID .. "/temperature",30,0,0, function(conn)
print ("temp published")
node.dsleep(10*1000000)
end)
end)
(init.lua)
tmr.alarm(1,500, 1, function()
if wifi.sta.getip()==nil
then
print(" Wait to IP address!")
else
print("New IP address is "..wifi.sta.getip())
dofile("mqtt.lua")
end
end)

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ESP8266 SDK and Toolchain
• I want to have more control / more speed / be
cool
• ESP8266 SDK available at bbs.espressif.com
• Espressif compiler in VM
• crosstool-NG on Win/Linux/Mac
github.com/pfalcon/esp-open-sdk
• Unofficial DevKit for ESP8266 (Windows) at
http://programs74.ru/udkew-en.html

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ESP8266 IoT SDK
• Low-level C SDK, partially open source
• Soft Timer
#define DELAY 100 /* milliseconds */
LOCAL os_timer_t blink_timer;
LOCAL void ICACHE_FLASH_ATTR blink_cb(void *arg)
{
GPIO_OUTPUT_SET(LED_GPIO, led_state);
led_state ^=1;
}
void user_init(void)
{
......
// Set up a timer to blink the LED
os_timer_disarm(&blink_timer);
os_timer_setfn(&blink_timer, (os_timer_func_t *)blink_cb, (void *)0);
os_timer_arm(&blink_timer, DELAY, 1);
}

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• Non-OS Task
#define recvTaskPrio 0
#define recvTaskQueueLen 10
os_event_t recvTaskQueue[recvTaskQueueLen];
void ICACHE_FLASH_ATTR uart_init()
{
system_os_task(recvTask, recvTaskPrio, recvTaskQueue, recvTaskQueueLen);
....
}
void uart0_rx_intr_handler(void *para)
{
....
system_os_post(recvTaskPrio, SIG_RX, RcvChar);
}
void recvTask(os_event_t *e)
{
switch (e->sig) {
case SIG_RX:
os_printf(“sig_rx %c/n”, (char)e->par);
break;
}
}

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•TCP/UDP APIs
void to_scan(*arg)
{
...
espconn_regist_connectcb(conn, connect_callback);
espconn_regist_disconcb(conn, disconnect_callback);
espconn_regist_reconcb(conn, error_callback);
espconn_connect(conn);
}
void connect_callback(void * arg)
{
espconn_regist_recvcb(conn, receive_callback);
espconn_regist_sentcb(conn, sent_callback);
}
void user_init(void)
{
wifi_set_opmode(STATION_MODE);
system_init_done_cb(to_scan);
}
Chain of callbacks, soon gets very messy

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RTOS SDK
• Partially open source at
https://github.com/espressif/esp_iot_rtos_sdk
• Based on FreeRTOS / lwip
• BSD sockets (thread-safe)
• Newer, clearer code
• Foundation of esp8266_iot_platform

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FreeRTOS
void blink_thread()
{
while(1)
{
toggle_led();
vTaskDelay(1000 / portTICK_RATE_MS);
}
}
void receive_thread()
{
while(1)
{
xQueueReceive(xQueueUart, (void *)&e, portMAX_DELAY);
...
}
}

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Example
wifi_thread
Set WiFi parameters
while (not no ip and not timeout)
{ vTaskDelay; }
while (have ip)
{
xSemaphoreGive(wifi_alive);
vTaskDelay;
}
wifi_disconnect();
vTaskDelay;
mqtt_thread
xSemaphoreTake(wifi_alive);
mqtt_connect
while (not fail)
{
if have message publish;
mqtt_yield(timeout);
}
mqtt_subscribe

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Demo

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Other resources
• www.espressif.com
• www.esp8266.com
• ESPlorer http://esp8266.ru/esplorer
• My favorite serial terminal Termite
http://www.compuphase.com/software_termite.htm
• Flash Download Tool http://bbs.espressif.com/

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About me
• www.ba0sh1.com
• mail@ba0sh1.com
• Twitter @ba0sh1
• https://www.facebook.com/baoshi