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Raspberry Pi 3 的新版本 Model B+

Raspberry Pi 3 推出了 Model B+ 的新版本:「Raspberry Pi 3 Model B+ on sale now at $35」。

除了 CPU 速度稍微快一些以外,另外支援了 802.11ac/5Ghz 的無線網路 (官方宣稱可以跑到 ~102Mbps,相較於先前在 2.4Ghz 只能跑到 ~35Mbps),以及更快的有線網路 (官方宣稱可以跑到 ~315Mbps,相較於先前的 ~95Mbps)。

然後是支援 PXE

Raspberry Pi 3B was our first product to support PXE Ethernet boot. Testing it in the wild shook out a number of compatibility issues with particular switches and traffic environments. Gordon has rolled up fixes for all known issues into the BCM2837B0 boot ROM, and PXE boot is now enabled by default.

以及支援 PoE 直接推動整台機器:

We use a magjack that supports Power over Ethernet (PoE), and bring the relevant signals to a new 4-pin header. We will shortly launch a PoE HAT which can generate the 5V necessary to power the Raspberry Pi from the 48V PoE supply.

或是吃更多電 XDDD

Note that Raspberry Pi 3B+ does consume substantially more power than its predecessor. We strongly encourage you to use a high-quality 2.5A power supply, such as the official Raspberry Pi Universal Power Supply.

所以看到這張圖時就不意外了 XDDD (風扇!)


Update:風扇那張圖的產品頁看起來在「Raspberry Pi PoE HAT」這頁 (參考下面的 comment)。

微軟的 Time Service 回應錯誤的時間...

看起來會有不少災情 (像是 SQL Server 遇到使用 server side 的時間的 SQL query):「Windows Time Service is sending out wrong times and that’s a big problem」,報導裡引用了 Reddit 上「PSA: time.windows.com NTP server seems to be sending out wrong time」這邊的討論串。

為了避免這種情況,不同單位會用不同方法解決。像是財力充足的 Google 就自己搞了原子鐘,然後還放 Google Public NTP 出來給大家用。可以不倚靠外部裝置確保自家時間的正確性。

另外是有人用 Raspberry Pi 收 GPS 訊號轉成 NTP service (像是「The Raspberry Pi as a Stratum-1 NTP Server」這邊介紹的方式),不過之前有發生過 GPS 送出來的時間差了 13ms 的事情,也不是完全可靠 (不過相較起來應該還是可以接受):「GPS error caused '12 hours of problems' for companies」。另外可能的方案有 GLONASS (俄羅斯的系統)。


Google 將 Raspberry Pi 3 加到 AOSP 裡

GoogleAOSP 裡加入對 Raspberry Pi 3 的支援:「Google to bring official Android support to the Raspberry Pi 3」,repository 可以在「device/pifoundation/rpi3/」這邊看到,目前是空的,不過這讓大家就有很多想像了:

For now, the Pi 3 device tree is empty with only the comment "initial empty repository" accompanying it. The repository should soon start to fill with code, though.

感覺對 Raspberry Pi 注入了不少活力... (以及估值 XDDD)

NASA 的 JPL 回答「你們用的圓周率是 3.14 嗎?」的問題

NASAJPL 回答了他們所使用的圓周率:「How Many Decimals of Pi Do We Really Need?」。


For JPL's highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793.

先拿目前離地球最遠的人造物 Voyager 1 來舉例,約 201 億公里 (125 億英里) 的距離,使用這個小數下 15 位的圓周率,與實際的圓周率算出來的誤差只有 3.81 公分 (1.5 英寸):

The most distant spacecraft from Earth is Voyager 1. It is about 12.5 billion miles away.

It turns out that our calculated circumference of the 25 billion mile diameter circle would be wrong by 1.5 inches. Think about that. We have a circle more than 78 billion miles around, and our calculation of that distance would be off by perhaps less than the length of your little finger.

另外還舉了地球與整個宇宙的數字來計算,需要的精確度沒有想像中那麼大 XD


在「Listening to satellites for 30 dollars」這篇文章介紹了如何接受氣象衛星的訊號,並且轉成圖片...

關鍵的兩個軟體,一個是作者是先用 GQRX 收下來,然後用 WXtoImg 轉成圖片,這是作者抓下來的成果:(NOAA-15 的資訊)

如果在刻一些程式儘量全自動化,用 Raspberry Pi 丟到陽台收訊號轉換,好像是個不錯的方法?不知道衛星每天丟出來的量有多少...

Raspberry Pi Zero

Raspberry Pi 出了新的系列,只要 USD$5 的 Raspberry Pi Zero:「Raspberry Pi Zero: the $5 computer - Raspberry Pi」。

機器更小了,不過要注意的是沒有網路介面。看起來比較像是接機器人之類的?先用 USB 裝一裝,裝好後就都不需要了...

  • A Broadcom BCM2835 application processor
    • 1GHz ARM11 core (40% faster than Raspberry Pi 1)
  • 512MB of LPDDR2 SDRAM
  • A micro-SD card slot
  • A mini-HDMI socket for 1080p60 video output
  • Micro-USB sockets for data and power
  • An unpopulated 40-pin GPIO header
    • Identical pinout to Model A+/B+/2B
  • An unpopulated composite video header
  • Our smallest ever form factor, at 65mm x 30mm x 5mm

用 Raspberry Pi 自幹一台 3G 手機...

在「DIY Smartphone」這邊看到用 Raspberry Pi 做出一台手機:

DIY Smartphone using Raspberry Pi A+ Pi, Camera, PiTFT, and Adafruit FONA with custom mobile OS.

然後 FAQ 的部份 XDDD

The thing is a inch thick! Why would you build something so useless when you can buy a cheap phone for less that can do much much more?

No reason.