Raspberry Pi: A Portable and Powerful Single Board Computer

Task 1
Raspberry pi
Raspberry pi is a portable and a single board computer, small in size (like that of a credit card),
and performs a range of tasks just like desktop computer. Raspberry pi is used for browsing,
playing video games, playing HD videos, processing word documents and making spreadsheets
(Upton, 2014). Raspberry pi has two models, model A and model B, the difference being on the
cost, Ethernet and USB ports. Figure 1 shows the architecture of raspberry pi. The components
can be decomposed into two parts, internal and external components.
Figure 1. Raspberry pi architecture
Internal components
Memory- raspberry pi program memory (RAM) varies with the model. First release of Model A
had 256MB of SDRAM whereas Model B had 51MB of the memory. The RAM memory is made
up of splits, allocated for CPU and GPU. For the normal personal computer, RAM memory
capacity is in gigabytes. Other releases of raspberry pi however have memory more than
256MB.
Central processing unit (CPU)- is the brain of the personal computer and is tasked to execute
instructions of the raspberry pi through logical operations. First generation raspberry pi had
Broadcom BCM2835 System on chip, with 700MHz ARM11 processor. Generally this type of
computer uses ARM11 series of processors.
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Graphics processing unit (GPU)- this is a chip in the board responsible for speeding up
mathematical calculations that results in image, video and animations creation. Raspberry pi
GPU uses ‘Broadcom video core IV’ (Maksimovic & Vujovic, 2014 ).
External components
Ethernet port- this is the main gateway port of the raspberry pi used for communication with
external devices. This is the port that is used to connect the home router for internet access.
LEDs- the light emitting diodes are used to indicate status of certain operations by a light in the
raspberry pi board
USB- USB is used to connect all types of peripheral devices to the raspberry pi for example
keyboard, mouse etc. Model A of the raspberry pi has one USB port and model B has two ports.
USB port can also be used in expanding the number of ports.
UART- abbreviation for Universal Asynchronous Receiver and Transmitter is the output and
input port of the raspberry pi. This port is used for serial data transfer in form of text. It also
used to convert debugging code
HDMI- this allows the user to attach high definition TV and other LCD devices to the raspberry
pi
SD card slot-SD card with operating system installed in it, to be used by the raspberry pi is
inserted through the slot
Power connector- 5 volts USB connector is used for supplying external power source into the
raspberry pi.
GPIO Pins- they are used for communication with other electronic boards. GPIO pins accepts
output and input commands as programmed in raspberry pi
Task 2
Memory is a device used for storing data and programs either temporarily or permanently, to
be used by a computer or other electronic devices (stalling, 2013). In computer systems there
are two types of memory, namely external and internal memory. Internal memory is where
small quantity of data is temporarily stored and can be directly and easily accessed by the CPU.
Most of the internal storage devices are volatile meaning upon power loss the data is lost.
There are three main types of internal memory namely RAM cache and ROM.
Random Access Memory
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This is the memory that holds data and programs that are in use while the computer the
operating so as to increase the speed at which it is accessed. It acts as intermediary between
the CPU and hard disk and this helps speed up the operation of a computer. Reading data in
RAM is faster that that stored in external memory. CPU is responsible for overwriting old data
in the RAM when full, so as not to slow down its operations. Its main characteristics are
 It’s a volatile memory
 Its expensive
 RAM reads and writes data at byte level
RAM comes in two types, static RAM and dynamic RAM. The differences are outlined in the
table 1
Table 1: DRAM versus SRAM
Dynamic RAM Static RAM
Its technology is based on capacitors Its technology is based on flip-flop
Used where small memory capacity is required Used where large memory capacity is required
Slower access time Faster access time
Read Only Memory
The memory is not volatile, found in chips and is primarily used for storing computer bios along
with other vital information. Its major characteristics are as shown below
 Data is written into it when manufacturing
 Once it has been programmed, ROM can never be erased
 ROM contents are only fixed during fabrication by metal masks
ROM is widely used in storing control programs, for permanent data storage, BIOS, embedded
system code among others
ROM comes in three types, EEPROM, EPROM and PROM
Cache memory
Cache memory is the fastest memory of the three main types acting as a buffer between
Random Access Memory and the central processing unit as shown in figure 2. Cache memory
stores data and instructions that are frequently used or requested by CPU so that they are
readily available when requested (Stalling 2014). General impact of cache memory is a
reduction in time used to access data from RAM.
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