树莓派zero w 使用AV接口连接电视机
树莓派zero本身板子上有一个mini HDMI，但是我看到好像板子上还有一个小接口，上面写着TV，感觉应该可以输出AV信号，于是网上搜索了一番，果然可以。
首先，手工做了一根线，将一个视频接口变成两个小接口；
然后，再树莓派上焊上插针；
最后，将接口连接起来，注意信号线和接地线，不要反了。
树莓派的TV插座上，底座是方口的是正级，圆口的是负级。对应电视机的莲花头外圈是负级，内柱是正级。
具体如图：
换个角度看一下：
线做好之后，就可以直接跟电视机的AV信号口连接了，由于只有视频信号，没有接声音，因此只要接电视机上的视频信号口就可以了，一般是黄色。
在树莓派上要进行一下配置才能输出视频。
配置文件位于 /boot/config.txt
核心配置：
sdtv_mode=2另外，要把 hdmi_ignore_hotplug=1 前面加上#，给注释掉，不要输出HDMI
此外，如果你还通过raspi-config等设置了分辨率之类的，也把相关的配置注释掉，例如
hdmi_group=2
hdmi_mode=82
等等。。。如果你不太清楚这些配置的含义，查看一下文章最后的网页。
要注意的是：HDMI好像不能和视频信号同时输出，所以在配置AV视频信号输出的时候，一定要把HDMI相关全部的内容注释掉。
这个我折腾了很久，还以为正负级接反了。
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总结
1、整体感觉显示效果一般，显示效果回到了FC游戏机年代
2、但是显示简单，兼容性好，连到老电视也能显示
3、与HDMI不能同时输出
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最终效果图
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附件：列几个配置文件里面video相关的内容，供参考。
RPiconfig - eLinux.org
https://elinux.org/RPiconfig
Video mode options
sdtv_mode defines the TV standard for composite output (default=0)
sdtv_mode=0 Normal NTSC sdtv_mode=1 Japanese version of NTSC – no pedestal sdtv_mode=2 Normal PAL sdtv_mode=3 Brazilian version of PAL – 525/60 rather than 625/50, different subcarrier
sdtv_aspect defines the aspect ratio for composite output (default=1)
sdtv_aspect=1 4:3 sdtv_aspect=2 14:9 sdtv_aspect=3 16:9
hdmi_safe Use "safe mode" settings to try to boot with maximum hdmi compatibility. This is the same as the combination of: hdmi_force_hotplug=1, hdmi_ignore_edid=0xa5000080, config_hdmi_boost=4, hdmi_group=2, hdmi_mode=4, disable_overscan=0, overscan_left=24, overscan_right=24, overscan_top=24, overscan_bottom=24
hdmi_safe=1
hdmi_force_hotplug Pretends HDMI hotplug signal is asserted so it appears a HDMI display is attached
hdmi_force_hotplug=1 Use HDMI mode even if no HDMI monitor is detected
hdmi_ignore_hotplug Pretends HDMI hotplug signal is not asserted so it appears a HDMI display is not attached
hdmi_ignore_hotplug=1 Use composite mode even if HDMI monitor is detected
hdmi_mode defines screen resolution in CEA or DMT format (for other modes not listed here have a look at this thread)
These values are valid if hdmi_group=1 (CEA) hdmi_mode=1 VGA hdmi_mode=2 480p 60 Hz hdmi_mode=3 480p 60 Hz H hdmi_mode=4 720p 60 Hz hdmi_mode=5 1080i 60 Hz hdmi_mode=6 480i 60 Hz hdmi_mode=7 480i 60 Hz H hdmi_mode=8 240p 60 Hz hdmi_mode=9 240p 60 Hz H hdmi_mode=10 480i 60 Hz 4x hdmi_mode=11 480i 60 Hz 4x H hdmi_mode=12 240p 60 Hz 4x hdmi_mode=13 240p 60 Hz 4x H hdmi_mode=14 480p 60 Hz 2x hdmi_mode=15 480p 60 Hz 2x H hdmi_mode=16 1080p 60 Hz hdmi_mode=17 576p 50 Hz hdmi_mode=18 576p 50 Hz H hdmi_mode=19 720p 50 Hz hdmi_mode=20 1080i 50 Hz hdmi_mode=21 576i 50 Hz hdmi_mode=22 576i 50 Hz H hdmi_mode=23 288p 50 Hz hdmi_mode=24 288p 50 Hz H hdmi_mode=25 576i 50 Hz 4x hdmi_mode=26 576i 50 Hz 4x H hdmi_mode=27 288p 50 Hz 4x hdmi_mode=28 288p 50 Hz 4x H hdmi_mode=29 576p 50 Hz 2x hdmi_mode=30 576p 50 Hz 2x H hdmi_mode=31 1080p 50 Hz hdmi_mode=32 1080p 24 Hz hdmi_mode=33 1080p 25 Hz hdmi_mode=34 1080p 30 Hz hdmi_mode=35 480p 60 Hz 4x hdmi_mode=36 480p 60 Hz 4xH hdmi_mode=37 576p 50 Hz 4x hdmi_mode=38 576p 50 Hz 4x H hdmi_mode=39 1080i 50 Hz reduced blanking hdmi_mode=40 1080i 100 Hz hdmi_mode=41 720p 100 Hz hdmi_mode=42 576p 100 Hz hdmi_mode=43 576p 100 Hz H hdmi_mode=44 576i 100 Hz hdmi_mode=45 576i 100 Hz H hdmi_mode=46 1080i 120 Hz hdmi_mode=47 720p 120 Hz hdmi_mode=48 480p 120 Hz hdmi_mode=49 480p 120 Hz H hdmi_mode=50 480i 120 Hz hdmi_mode=51 480i 120 Hz H hdmi_mode=52 576p 200 Hz hdmi_mode=53 576p 200 Hz H hdmi_mode=54 576i 200 Hz hdmi_mode=55 576i 200 Hz H hdmi_mode=56 480p 240 Hz hdmi_mode=57 480p 240 Hz H hdmi_mode=58 480i 240 Hz hdmi_mode=59 480i 240 Hz H H means 16:9 variant (of a normally 4:3 mode). 2x means pixel doubled (that is, higher clock rate, with each pixel repeated twice) 4x means pixel quadrupled (that is, higher clock rate, with each pixel repeated four times)
These values are valid if hdmi_group=2 (DMT) Note: according to Does RPi support resolution of 2560x1440? - Raspberry Pi Forums there is a pixel clock limit which means the highest supported mode is 1920x1200 @60 Hz with reduced blanking. hdmi_mode=1 640x350 85 Hz hdmi_mode=2 640x400 85 Hz hdmi_mode=3 720x400 85 Hz hdmi_mode=4 640x480 60 Hz hdmi_mode=5 640x480 72 Hz hdmi_mode=6 640x480 75 Hz hdmi_mode=7 640x480 85 Hz hdmi_mode=8 800x600 56 Hz hdmi_mode=9 800x600 60 Hz hdmi_mode=10 800x600 72 Hz hdmi_mode=11 800x600 75 Hz hdmi_mode=12 800x600 85 Hz hdmi_mode=13 800x600 120 Hz hdmi_mode=14 848x480 60 Hz hdmi_mode=15 1024x768 43 Hz DO NOT USE hdmi_mode=16 1024x768 60 Hz hdmi_mode=17 1024x768 70 Hz hdmi_mode=18 1024x768 75 Hz hdmi_mode=19 1024x768 85 Hz hdmi_mode=20 1024x768 120 Hz hdmi_mode=21 1152x864 75 Hz hdmi_mode=22 1280x768 Reduced blanking hdmi_mode=23 1280x768 60 Hz hdmi_mode=24 1280x768 75 Hz hdmi_mode=25 1280x768 85 Hz hdmi_mode=26 1280x768 120 Hz Reduced blanking hdmi_mode=27 1280x800 Reduced blanking hdmi_mode=28 1280x800 60 Hz hdmi_mode=29 1280x800 75 Hz hdmi_mode=30 1280x800 85 Hz hdmi_mode=31 1280x800 120 Hz Reduced blanking hdmi_mode=32 1280x960 60 Hz hdmi_mode=33 1280x960 85 Hz hdmi_mode=34 1280x960 120 Hz Reduced blanking hdmi_mode=35 1280x1024 60 Hz hdmi_mode=36 1280x1024 75 Hz hdmi_mode=37 1280x1024 85 Hz hdmi_mode=38 1280x1024 120 Hz Reduced blanking hdmi_mode=39 1360x768 60 Hz hdmi_mode=40 1360x768 120 Hz Reduced blanking hdmi_mode=41 1400x1050 Reduced blanking hdmi_mode=42 1400x1050 60 Hz hdmi_mode=43 1400x1050 75 Hz hdmi_mode=44 1400x1050 85 Hz hdmi_mode=45 1400x1050 120 Hz Reduced blanking hdmi_mode=46 1440x900 Reduced blanking hdmi_mode=47 1440x900 60 Hz hdmi_mode=48 1440x900 75 Hz hdmi_mode=49 1440x900 85 Hz hdmi_mode=50 1440x900 120 Hz Reduced blanking hdmi_mode=51 1600x1200 60 Hz hdmi_mode=52 1600x1200 65 Hz hdmi_mode=53 1600x1200 70 Hz hdmi_mode=54 1600x1200 75 Hz hdmi_mode=55 1600x1200 85 Hz hdmi_mode=56 1600x1200 120 Hz Reduced blanking hdmi_mode=57 1680x1050 Reduced blanking hdmi_mode=58 1680x1050 60 Hz hdmi_mode=59 1680x1050 75 Hz hdmi_mode=60 1680x1050 85 Hz hdmi_mode=61 1680x1050 120 Hz Reduced blanking hdmi_mode=62 1792x1344 60 Hz hdmi_mode=63 1792x1344 75 Hz hdmi_mode=64 1792x1344 120 Hz Reduced blanking hdmi_mode=65 1856x1392 60 Hz hdmi_mode=66 1856x1392 75 Hz hdmi_mode=67 1856x1392 120 Hz Reduced blanking hdmi_mode=68 1920x1200 Reduced blanking hdmi_mode=69 1920x1200 60 Hz hdmi_mode=70 1920x1200 75 Hz hdmi_mode=71 1920x1200 85 Hz hdmi_mode=72 1920x1200 120 Hz Reduced blanking hdmi_mode=73 1920x1440 60 Hz hdmi_mode=74 1920x1440 75 Hz hdmi_mode=75 1920x1440 120 Hz Reduced blanking hdmi_mode=76 2560x1600 Reduced blanking hdmi_mode=77 2560x1600 60 Hz hdmi_mode=78 2560x1600 75 Hz hdmi_mode=79 2560x1600 85 Hz hdmi_mode=80 2560x1600 120 Hz Reduced blanking hdmi_mode=81 1366x768 60 Hz hdmi_mode=82 1080p 60 Hz hdmi_mode=83 1600x900 Reduced blanking hdmi_mode=84 2048x1152 Reduced blanking hdmi_mode=85 720p 60 Hz hdmi_mode=86 1366x768 Reduced blanking