Getting Started with Python for the Internet of Things

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How to do it...

The layout of Raspberry Pi is shown in the following diagram:

The Raspberry Pi connection layout (Model 3 B, Model A+, and Pi Zero)

More information about the preceding figure is listed as follows:

Display: The Raspberry Pi supports the following three main display connections; if both HDMI and composite video are connected, it will default to HDMI only:
- HDMI: For best results, use a TV or monitor that has an HDMI connection, thus allowing the best resolution display (1080p) and also digital audio output. If your display has a DVI connection, you may be able to use an adapter to connect through the HDMI. There are several types of DVI connection; some support analogue (DVI-A), some digital (DVI-D), and some both (DVI-I). Raspberry Pi is only able to provide a digital signal through the HDMI, so an HDMI-to-DVI-D adapter is recommended (shown with a tick mark in the following screenshot). This lacks the four extra analogue pins (shown with a cross mark in the following screenshot), thus allowing it to fit into both DVI-D and DVI-I type sockets:

HDMI-to-DVI connection (DVI-D adaptor)

If you wish to use an older monitor (with a VGA connection), an additional HDMI-to-VGA converter is required. Raspberry Pi also supports a rudimentary VGA adaptor (VGA Gert666 Adaptor), which is driven directly off of the GPIO pins. However, this does use up all but four pins of the 40-pin header (older 26-pin models will not support the VGA output):

HDMI-to-VGA adapter

- Analogue: An alternative display method is to use the analogue composite video connection (via the phono socket); this can also be attached to an S-Video or European SCART adapter. However, the analogue video output has a maximum resolution of 640 x 480 pixels, so it is not ideal for general use:

3.5 mm phono analogue connections

When using the RCA connection or a DVI input, audio has to be provided separately by the analogue audio connection. To simplify the manufacturing process (by avoiding through-hole components), the Pi Zero does not have analogue audio or an RCA socket for analogue video (although they can be added with some modifications):

- Direct Display DSI: A touch display produced by Raspberry Pi Foundation will connect directly into the DSI socket. This can be connected and used at the same time as the HDMI or analogue video output to create a dual display setup.
Stereo analogue audio (all except Pi Zero): This provides an analogue audio output for headphones or amplified speakers. The audio can be switched via Raspberry Pi configuration tool on the desktop between analog (stereo socket) and digital (HDMI), or via the command line using amixer or alsamixer.

To find out more information about a particular command in the Terminal, you can use the following man command before the terminal reads the manual (most commands should have one):

man amixer

Some commands also support the --help option for more concise help, shown as follows:

amixer --help

Network (excluding models A and Pi Zero): The network connection is discussed in the Networking and connecting your Raspberry Pi to the internet via the LAN connector recipe later in this chapter. If we use the Model A Raspberry Pi, it is possible to add a USB network adapter to add wired or even wireless networking (refer to the Networking and connecting your Raspberry Pi to the internet via a USB Wi-Fi dongle recipe).
Onboard Wi-Fi and Bluetooth (Model 3 B only): The Model 3 B has built-in 802.11n Wi-Fi and Bluetooth 4.1; see the Using the built-in Wi-Fi and Bluetooth on Raspberry Pi recipe.
USB (1x Model A/Zero, 2x Model 1 B, 4x Model 2 B and 3 B): Using a keyboard and mouse:
- Raspberry Pi should work with most USB keyboards and mice. You can also use wireless mice and keyboards, which use RF dongles. However, additional configuration is required for items that use the Bluetooth dongles.
- If there is a lack of power supplied by your power supply or the devices are drawing too much current, you may experience the keyboard keys appearing to stick, and, in severe cases, corruption of the SD card.

USB power can be more of an issue with the early Model B revision 1 boards that were available prior to October 2012. They included additional Polyfuses on the USB output and tripped if an excess of 140 mA was drawn. The Polyfuses can take several hours or days to recover completely, thus causing unpredictable behavior to remain even when the power is improved.

You can identify a revision 1 board, as it lacks the four mounting holes that are present in the later models.

- Debian Linux (upon which Raspbian is based) supports many common USB devices, such as flash storage drives, hard-disk drives (external power may be required), cameras, printers, Bluetooth, and Wi-Fi adapters. Some devices will be detected automatically, while others will require drivers to be installed.

Micro USB power: The Raspberry Pi requires a 5V power supply that can comfortably supply at least 1,000 mA (1,500 mA or more is recommended, particularly with the more power-hungry Model 2 and Model 3) with a micro USB connection. It is possible to power the unit using portable battery packs, such as the ones suitable for powering or recharging tablets. Again, ensure that they can supply 5V at 1,000 mA or over.

You should aim to make all other connections to Raspberry Pi before connecting the power. However, USB devices, audio, and networks may be connected and removed while it is running, without problems.