Some time ago I decided to become more familiar with Internet of things. I thought about several projects, but I didn't decide what to do this is why I bought several things and forgot about them for a while.
Few days ago I decided to take a look inside. Newbies (like me) think that pieces for the project could be expensive, actually they are not so. I decided to publish what I bought and how much it cost.
- Electronic Parts Pack KIT for ARDUINO component Resistors Switch Button WT, Price – 3.70 USD
- Soil Hygrometer Humidity Detection Module Soil Moisture Water Sensor, Price – 1.16 USD
- MB102 Power Supply Module 3.3V 5V+Breadboard Board 830 Point+65PCS Jumper cable, Price – 5.08 USD
- DHT22 AM2302 Digital Temperature and Humidity Sensor module Replace SHT11 SHT15, Price – 5.97 USD
- UNO R3 ATmega328P CH340 Mini USB Board for Compatible-Arduino NEW, Price – 3.95 USD
- Raspberry Pi-2 + Acrylic Enclosure Case + Heat sink, Price – 42.27 USD
- Micro USB Charger 5V, 2A, Price – 7.64 USD
- Temperature sensor DS18b20 in iron case, Price – 1.25 USD
- Micro SD memory card Class 10 Size 8GB , Price – 5.17 USD
- Wi-Fi USD Adapter EDUP EP-N8508GS, Price – 5.66 USD
Let's start with something. I went to the https://www.raspberrypi.org/ and found that I have to copy operating system to the SD card and insert SD card to the raspberry. Ok I decided to load NOOBS OS and after that select raspbian OS. I bought Class 10 SD card (fast SD Card ). After I inserted card in the raspberry and connect via HDMI raspberry I found that nothing is printed on screen. First attempt fail, the good idea was to consult here the list of compatible SD card before to buy something. Ok I found at home old SD card at 8 Gb and I decided to try it just for proof of concept. Second attempt was good.
To configure raspberry you have to get USB mouse and Keyboard. Nothing of those I have in the house. After several hours I found only mouse. Ok let's start with this, especially that on first stage I have only to select OS and boot raspberry. After boot I got the screen with GUI and I still don't have keyboard. Probably I could connect via ssh to OS was my idea. I could do it in two ways via LAN or WLAN. My Home router has password, so even wi-fi card is up raspberry doesn't know my password. I connected laptop to device via LAN, bring up on laptop DHCP server (tftpf32 could do it very fast), found which ip address was leased to raspberry and connects to him via putty (default user: pi, password: raspberry). Everything is easy here I thought. Let's connect raspberry to wi-fi. I have never been connect linux to wi-fi before. It's shouldn't be too difficult, especially that I am connecting linux via LAN in a day by day activities. Spent some time on google I found a lot of step-by-step instructions and different options, but no one work for me.
My Wi-Fi Card is:
pi@raspberrypi:~ $ lsusb
Bus 001 Device 004: ID 0bda:8176 Realtek Semiconductor Corp. RTL8188CUS 802.11n WLAN Adapter
My OS is:
pi@raspberrypi:~ $ cat /etc/*release
PRETTY_NAME="Raspbian GNU/Linux 8 (jessie)"
After several hours I start to hate Linux and I saw that I am not single in this feeling. How can so easy task take so much time? I started my attempts with wireless-tools installed on raspbian. Command iwlist wlan0 scan provides info about my router. This means that driver for wlan0 interface was installed and interface is up. Let's try connect manually to router using: iwconfig wlan0 essid <YOUR_SSID> key s:<Your password>. Several attemps fail. Ok let's try to use another option. I found that wpa_supplicant was created especially for people who want to use Wi-FI in secure way and has WPA2 encryption. Command wpa_passphrase <Your_SSID> <Your_Password> >> /etc/wpa_supplicant/wpa_supplicant.conf will create config file for your Network and save password in the safe way. If select wpa_supplicant method you have to fill /etc/network/interfaces with something like this:
iface wlan0 inet manual
Inet manual is required by wpa_supplicant even you have to use dhcp. If you want dhcp do this:
iface wlan0 inet manual
iface default inet dhcp
I created wpa_supplicant config for me, checked /etc/network/interfaces but I still couldn't associate with Wi-Fi. After several attempts I tried to run wpa_supplicant daemoon manually. This part I want to share with you in more details. After network service restart (/etc/init.d/networking restart) in the background is started wpa_supplicant daemoon. Command ps aux | grep wpa* provides me the following:
/sbin/wpa_supplicant -s -B -P /run/wpa_supplicant.wlan0.pid -i wlan0 -D nl80211,wext -c /etc/wpa_supplicant/wpa_supplicant.conf
This still doesn't help me. Somewhere should be the log files. Yes they are in /var/log/syslog or /var/log/messages or /var/log/wpa_supplicant.log. For me it was /var/log/syslog. Inside I found that:
nl80211: Driver does not support authentication/association or connect commands
Hmm, let's kill the process and play manually with different options, drivers of wpa_supplicant.
Sometimes I could get another error:
wlan0: CTRL-EVENT-SSID-TEMP-DISABLED id=0 ssid="Home" auth_failures=11 duration=120 reason=CONN_FAILED
I edited several times wpa_supplicant.conf file with different options and at the end I got something like this:
root@raspberrypi:/home/pi# cat /etc/wpa_supplicant/wpa_supplicant.conf
#psk=8d0526f31a39e78dfgk;srs61ae5a1e9d0c30e8e48cc838f8541d4a8e7af259 #password generated by wpa_passphrase
At the beginning I had only ssid and psk key generated by wpa_passphrase. Information about key_mgmt, pairwise you could get using iwlist wlan0 scan command. Even everything seems to be logic I still couldn’t connect to the Router and get ip address from him. This is why I tried to launch manually supplicant using debug options:
/sbin/wpa_supplicant -s -B -P /run/wpa_supplicant.wlan0.pid -i wlan0 -D nl80211,wext -c /etc/wpa_supplicant/wpa_supplicant.conf -dd
Debug options and /var/log/syslog will give you information what failed for you. Each new option enabled/disabled in wpa_supplicant.conf file and drivers used in command provide new error to my investigation. It's interesting, but didn't help. Try to see in your case this.
Some instructions proposed to change /etc/network/interfaces in different way to connect raspberry to wi-fi. I have new way to investigate. I saw that someone is saying to use wpa-ssid, someone wpa-essid and different things. Why options are different? Let's try all of them :). It's good idea but this still didn't solve the issue. Windows seems to be better was my idea. Trying to find solution for me I found very interesting article written by mrEngman. Inside he shares his script how to configure wi-fi cards based on RTL8188CUS. I decided to read script instead to launch him (thanks author for very good comments inside). And there I found that wpa-ssid is for Router without authentication. For those with autehntication should be wpa-essid. wpa-psk should be used when you have WPA2 (most used), in case you have WEP you shold use wpa-key. Thanks to mrEngman that he decided to explain what means different options. After I edited /etc/network/interfaces like below everything started to work for me.
iface wlan0 inet dhcp
Conclusion: "Never give up!". Linux could be awful at first meet, but when you start to understand and think what is the impact of command, where to see logs, what means your options (use man pages), how to restart process manually and apply changes it becomes logic.
Important: Don't use at the same time iwconfig, wpa_supplicant. Select one method or script and debug it. Remember that processes are running in background and applied commands could affect actual results.