[OpenCV] 數字辨識

Digit Recognition
https://github.com/bikz05/digit-recognition

[OpenCV] 好站推

 "阿洲的程式教學" 分類不錯：http://monkeycoding.com/?page_id=12
"Notes of openCV-Python" 直接有範例看結果：http://blog.ganyutao.com/python/2016/01/11/Notes_of_python_openCV/

[RPi] 將Pi 3設成Wireless Router

1. 安裝必要軟體

$ sudo apt-get install isc-dhcp-server

$ sudo apt-get install hostapd

2. 備份阿

$ cd ~

$ mkdir bak

$ cp /etc/network/interfaces ~/bak

$ cp /etc/dhcp/dhcpd.conf ~/bak

$ cp /etc/hostapd/hostapd.conf ~/bak

3. 修改網路介面設定

$ sud vim /etc/network/interfaces

source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

allow-hotplug wlan0
iface wlan0 inet manual

4. 修改 dhcp server 設定

$ sudo vim /etc/dhcp/dhcpd.conf

ddns-update-style none;
option domain-name "my.raspberry.pi";
option domain-name-servers 8.8.8.8, 8.8.4.4;
default-lease-time 600;
max-lease-time 7200;
authoritative;
log-facility local7;
subnet 192.168.55.0 netmask 255.255.255.0 {
        range 192.168.55.101 192.168.55.200;
        option routers 192.168.55.1;
}

5. 修改 hostapd 設定

$ sudo vim /etc/hostapd/hostapd.conf

# This is the name of the WiFi interface we configured above
interface=wlan0
# Use the nl80211 driver with the brcmfmac driver
driver=nl80211
# This is the name of the network
ssid=Pi3-AP
# Use the 2.4GHz band
hw_mode=g
# Use channel 6
channel=6
# Enable 802.11n
ieee80211n=1
# Enable WMM
wmm_enabled=1
# Enable 40MHz channels with 20ns guard interval
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]
# Accept all MAC addresses
macaddr_acl=0
# Use WPA authentication
auth_algs=1
# Require clients to know the network name
ignore_broadcast_ssid=0
# Use WPA2
wpa=2
# Use a pre-shared key
wpa_key_mgmt=WPA-PSK
# The network passphrase
wpa_passphrase=1234567890
# Use AES, instead of TKIP
rsn_pairwise=CCMP

6. 建立啟動腳本

$ vim ~/ap_mode.sh

#!/bin/bash

ifconfig wlan0 192.168.55.1 netmask 255.255.255.0
iptables -A INPUT -i wlan0 -j ACCEPT
iptables -t nat -A POSTROUTING -s 192.168.55.0/24 -o eth0 -j MASQUERADE
sysctl net.ipv4.ip_forward=1
hostapd /etc/hostapd/hostapd.conf -B
dhcpd wlan0

7. 修改權限 & 設定開機就啟動

$ chmod 755 ~/ap_mode.sh

$ sudo vim /etc/rc.local

新增這行

sudo ~/ap_mode.sh

Reference:
* Using your new Raspberry Pi 3 as a WiFi access point with hostapd

[Tips] 列出連到哪一台 Wireless Router?

困擾已久, 已解決

$ iwconfig

wlan0     IEEE 802.11abgn  ESSID:"OWEN"  
          Mode:Managed  Frequency:2.412 GHz  Access Point: XX:XX:XX:XX:XX:XX   
          Bit Rate=144.4 Mb/s   Tx-Power=15 dBm   
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Power Management:off
          Link Quality=70/70  Signal level=-17 dBm  
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:10429  Invalid misc:42   Missed beacon:0

[Python] Locks, Mutexes, and Semaphores: Types of Synchronization Objects

好文參考：Locks, Mutexes, and Semaphores: Types of Synchronization Objects

[Python] Tkinter

" Wrapper functions for Tcl/Tk.

source:
http://mgltools.scripps.edu/api/DejaVu/Tkinter-pysrc.html 

document:
https://docs.python.org/2/library/tkinter.html

[Python] Threading

好文：Python线程同步机制: Locks, RLocks, Semaphores, Conditions, Events和Queues