树莓派|树莓派zero w 使用AV接口连接电视机 python|物联网

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：

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换个角度看一下：

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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

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https://elinux.org/RPiconfig
Video mode options sdtv_mode defines the TV standard for composite output (default=0)

sdtv_mode=0Normal NTSC sdtv_mode=1Japanese version of NTSC – no pedestal sdtv_mode=2Normal PAL sdtv_mode=3Brazilian version of PAL – 525/60 rather than 625/50, different subcarrier

sdtv_aspect defines the aspect ratio for composite output (default=1)

sdtv_aspect=14:3 sdtv_aspect=214:9 sdtv_aspect=316:9

【树莓派|树莓派zero w 使用AV接口连接电视机】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=1VGA hdmi_mode=2480p60 Hz hdmi_mode=3480p60 HzH hdmi_mode=4720p60 Hz hdmi_mode=51080i60 Hz hdmi_mode=6480i60 Hz hdmi_mode=7480i60 HzH hdmi_mode=8240p60 Hz hdmi_mode=9240p60 HzH hdmi_mode=10480i60 Hz4x hdmi_mode=11480i60 Hz4x H hdmi_mode=12240p60 Hz4x hdmi_mode=13240p60 Hz4x H hdmi_mode=14480p60 Hz2x hdmi_mode=15480p60 Hz2x H hdmi_mode=161080p60 Hz hdmi_mode=17576p50 Hz hdmi_mode=18576p50 HzH hdmi_mode=19720p50 Hz hdmi_mode=201080i50 Hz hdmi_mode=21576i50 Hz hdmi_mode=22576i50 HzH hdmi_mode=23288p50 Hz hdmi_mode=24288p50 HzH hdmi_mode=25576i50 Hz4x hdmi_mode=26576i50 Hz4x H hdmi_mode=27288p50 Hz4x hdmi_mode=28288p50 Hz4x H hdmi_mode=29576p50 Hz2x hdmi_mode=30576p50 Hz2x H hdmi_mode=311080p50 Hz hdmi_mode=321080p24 Hz hdmi_mode=331080p25 Hz hdmi_mode=341080p30 Hz hdmi_mode=35480p60 Hz4x hdmi_mode=36480p60 Hz4xH hdmi_mode=37576p50 Hz4x hdmi_mode=38576p50 Hz4x H hdmi_mode=391080i50 Hzreduced blanking hdmi_mode=401080i 100 Hz hdmi_mode=41720p100 Hz hdmi_mode=42576p100 Hz hdmi_mode=43576p100 HzH hdmi_mode=44576i100 Hz hdmi_mode=45576i100 HzH hdmi_mode=461080i 120 Hz hdmi_mode=47720p120 Hz hdmi_mode=48480p120 Hz hdmi_mode=49480p120 HzH hdmi_mode=50480i120 Hz hdmi_mode=51480i120 HzH hdmi_mode=52576p200 Hz hdmi_mode=53576p200 HzH hdmi_mode=54576i200 Hz hdmi_mode=55576i200 HzH hdmi_mode=56480p240 Hz hdmi_mode=57480p240 HzH hdmi_mode=58480i240 Hz hdmi_mode=59480i240 HzH 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=1640x35085 Hz hdmi_mode=2640x40085 Hz hdmi_mode=3720x40085 Hz hdmi_mode=4640x48060 Hz hdmi_mode=5640x48072 Hz hdmi_mode=6640x48075 Hz hdmi_mode=7640x48085 Hz hdmi_mode=8800x60056 Hz hdmi_mode=9800x60060 Hz hdmi_mode=10800x60072 Hz hdmi_mode=11800x60075 Hz hdmi_mode=12800x60085 Hz hdmi_mode=13800x600120 Hz hdmi_mode=14848x48060 Hz hdmi_mode=151024x76843 HzDO NOT USE hdmi_mode=161024x76860 Hz hdmi_mode=171024x76870 Hz hdmi_mode=181024x76875 Hz hdmi_mode=191024x76885 Hz hdmi_mode=201024x768120 Hz hdmi_mode=211152x86475 Hz hdmi_mode=221280x768Reduced blanking hdmi_mode=231280x76860 Hz hdmi_mode=241280x76875 Hz hdmi_mode=251280x76885 Hz hdmi_mode=261280x768120 HzReduced blanking hdmi_mode=271280x800Reduced blanking hdmi_mode=281280x80060 Hz hdmi_mode=291280x80075 Hz hdmi_mode=301280x80085 Hz hdmi_mode=311280x800120 HzReduced blanking hdmi_mode=321280x96060 Hz hdmi_mode=331280x96085 Hz hdmi_mode=341280x960120 HzReduced blanking hdmi_mode=351280x102460 Hz hdmi_mode=361280x102475 Hz hdmi_mode=371280x102485 Hz hdmi_mode=381280x1024 120 HzReduced blanking hdmi_mode=391360x76860 Hz hdmi_mode=401360x768120 HzReduced blanking hdmi_mode=411400x1050Reduced blanking hdmi_mode=421400x105060 Hz hdmi_mode=431400x105075 Hz hdmi_mode=441400x105085 Hz hdmi_mode=451400x1050 120 HzReduced blanking hdmi_mode=461440x900Reduced blanking hdmi_mode=471440x90060 Hz hdmi_mode=481440x90075 Hz hdmi_mode=491440x90085 Hz hdmi_mode=501440x900120 HzReduced blanking hdmi_mode=511600x120060 Hz hdmi_mode=521600x120065 Hz hdmi_mode=531600x120070 Hz hdmi_mode=541600x120075 Hz hdmi_mode=551600x120085 Hz hdmi_mode=561600x1200 120 HzReduced blanking hdmi_mode=571680x1050Reduced blanking hdmi_mode=581680x105060 Hz hdmi_mode=591680x105075 Hz hdmi_mode=601680x105085 Hz hdmi_mode=611680x1050 120 HzReduced blanking hdmi_mode=621792x134460 Hz hdmi_mode=631792x134475 Hz hdmi_mode=641792x1344 120 HzReduced blanking hdmi_mode=651856x139260 Hz hdmi_mode=661856x139275 Hz hdmi_mode=671856x1392 120 HzReduced blanking hdmi_mode=681920x1200Reduced blanking hdmi_mode=691920x120060 Hz hdmi_mode=701920x120075 Hz hdmi_mode=711920x120085 Hz hdmi_mode=721920x1200 120 HzReduced blanking hdmi_mode=731920x144060 Hz hdmi_mode=741920x144075 Hz hdmi_mode=751920x1440 120 HzReduced blanking hdmi_mode=762560x1600Reduced blanking hdmi_mode=772560x160060 Hz hdmi_mode=782560x160075 Hz hdmi_mode=792560x160085 Hz hdmi_mode=802560x1600 120 HzReduced blanking hdmi_mode=811366x76860 Hz hdmi_mode=821080p60 Hz hdmi_mode=831600x900Reduced blanking hdmi_mode=842048x1152Reduced blanking hdmi_mode=85720p60 Hz hdmi_mode=861366x768Reduced blanking