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The Pi's (Read 1287 times)
Fernando
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The Pi's
Oct 22nd, 2014, 10:48am  
Since the late 1970s, there have been many Small Board Computer Systems (SBCs) of one design or another, with none really taking off in popularity because of their intense needs before becoming useful. Not many of us out there can remember the KYM and SYM SBCs made by Commodore and Rockwell (respectively).
 
But as of lately, there has been a surge in SBC systems in the Educational Market, first starting at the University level and trickling down to the Secondary School level and now onto the general population. These SBCs still need some work to get them running but with the general population now used to setting up their own PCs, such work is now acceptable.
 
The most popular of these SBCs today is the Raspberry Pi, created in the Great Britain and the UK for its educational market, it is priced to be sold at under $35. But that do you get for $35?

  • A credit card sized computer system with a "System on a Chip" (SoC) which contains CPU, 512MB RAM and High End Video and Audio.
  • The CPU is an ARM 10 CPU by ARM Semiconductors, a company that has been around since the 1970. The CPU runs at 700MHz and can be overclocked to 1.2GHz with the right precautions taken.
  • It has Basic I/O of USB Ports and a 10/100 Ethernet Port. It also has a GPIO Expansion area for connecting various electronics with it. The GPIO is User Programmable.
  • The whole system runs on 5 volts at under 2 amps, anything more could damage the board. But the Power Supply is sold separately.

 
There are various OSes for the Raspberry Pi, most taking the form of some version of Linux, and there are 2 proprietary OS made by ARMs Semiconductors. These have to be installed onto an SD Memory card of 8GB or more. Once installed, the SD Card becomes your system's hard drive".
 
Not included when you buy a Raspberry Pi are:
  • Keyboard and mouse. It is recommended you get a Bluetooth KB and Mouse as the Wireless adapter takes up less power than plugging in an actual USB KB and Mouse.
  • 5 volt Power Supply with a mini USB jack to plug in the board.
  • An SD Card for the OS, though you buy pre-installed SD Cards from your R-Pi store.
  • The OS, which needs to be downloaded from the RaspberryPi.org website. Again, you can buy an SD with the OS already installed.
  • Cables to connected to your HDMI Monitor.

 
This is just the basics in what you need to have a Raspberry Pi. And the Raspberry Pi is not the only SBC out there, but it is the most popular one due to its low price, insertion into the Educational Market and mass availability. Though made in the UK, China has begun cloning the Raspberry Pie for its markets and export. Whether this is allowed by contract by the makers of the Raspberry Pi or not, I do not know.
 
Banana Pi, BeagleBone, Odroid, Minnow, and many others are SBCs that has recently entered the market with each having their own cpu systems and designs to them while being able to run similar OSes, mostly some form of Linux. Banana Pi is a Chinese version of an update Raspberry Pi with dual core Arm 11 CPU instead of the single core A10 used on the Raspberry Pi, and though it can run the Raspberry Pi OSes, it is designed not to deliberately as to take advantage of the Dual Core CPU capabilities.
 
Further details will be added on this thread.
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« Last Edit: Oct 23rd, 2014, 7:49pm by Fernando »  
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Fernando
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Re: The Pi's
Reply #1 - Oct 22nd, 2014, 11:09am  
The OS
 
As stated before there are many OSes from which you can run your Pi with, they can be downloaded from the website or bought separately from the Pi Reseller.
 
The Raspberry PI OS Choices (downloadable from http://www.raspberrypi.org/downloads/ ):
  • NOOBs - a collection of OSes on a single download. Once loaded into the SD and run, it will ask you which OS to install and it will do much of the set up for you.
  • Raspian - a Debian Kernel Linux which is used on many Linux Distributions like Knoppix and Ubuntu.
  • Pidora - a Red Hat/Fedora Kernel Linux which is used on many distributions like Mint.
  • OPENELEC - An XBMC Media Center, if you want your Pi to be a Multimedia Center, this would do it.
  • RASPBMC - An XBMC Media Center, if you want your Pi to be a Multimedia Center, this would do it.
  • RISC OS - a Non-Linux OS originally made by ARM Semiconductor for their larger systems.

 
Other OSes exist for the Raspberry Pi, which are not part of this download group but still usable. Suse Pi is a version of Suse Linux for the Raspberry Pi available from Open Suse's website.
 
On other SBCs, there are other OSes available to them, like Google's Android. But due to different CPU architectures, many programs for these SBCs have to be recompiled to run on them. This creates a large software library for you to access and use when they are available.
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Re: The Pi's
Reply #2 - Oct 22nd, 2014, 11:27am  
Raspberry Pi Clones:
 
As stated before, the Raspberry Pi is being cloned in China. As far as I can tell there are at least 3 or 4 different Raspberry Pi's out there. Preferable you want to get the UK Raspberry Pi.
 
There is a Youtube comparing one of them to the UK Version:
https://www.youtube.com/watch?v=qP4qoVnhAEY
 
Raspberry Pi.org's forum discussion of couple of Chinese Clones:
http://www.raspberrypi.org/forums/viewtopic.php?f=63&t=37843
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Re: The Pi's
Reply #3 - Oct 22nd, 2014, 11:48am  
Evolution of the Raspberry Pi:
 
Since under development for the Educational Market since 2004, the Raspberry Pi has undergone many changes to its three main versions: the Model A, Model B and Model B+.
 
Due to its naming, one would figure that the Model A came out first. Though it was developed first when a final design was agreed on and tested, the Model B was released first to see if there was enough interest for the Raspberry Pi. The Model A was then sold once the Model B took a foothold in the Educational market a couple of months later at a lower price of around $25. Since 2006 to 2008, these were the only two Raspberry Pi's out.
 
The Model A had 1 USB Port, 256MB of RAM and did not have an Ethernet Port.
 
The Model B (ver 1) had 2 USB Port, 512MB of RAM and an Ethernet Port. It came in either a green or red PCB Board
 
Both were nearly identical electronically, using the same chips minus the differences.
 
In 2008, the Model B (ver 2) underwent some slight revision, board redesign and chip change for a slightly more power efficient but same chip. These changes were minor but noticeable. They all came green PCB boards.
 
In the Summer of 2011 a new version of the Model B was slated and then released in the Summer of 2014. It comes with a larger GPIO, more power efficient chips and 4 USB Ports. It is called the Model B+. At the time of the Model B+ Design, the Model A was discontinued.
 
There are now two versions of the Raspberry Pi out there, the Model B (which is also being cloned in China) and the Model B+. Both are on sold for under $40. Though 100% software compatible, they are not 100% hardware compatible - as the GPIO and other things were expanded and moved on the Model B+ board. This requires some modification of hardware used on the Model B to be used on the Model B+, like cutting, reshaping or rewiring the hardware in question. Some things can not be changed like the Model B+ using a MicroSD and the Model B using a full sized SD, though with an adapter the Model B can use a MicroSD. This allows the Model B to be used to create a MicroSD with an OS installed on it for the Model B+ since they are 100% software compatible.
 
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Re: The Pi's
Reply #4 - Oct 22nd, 2014, 12:29pm  
Issues I have noticed:
 
1)
Though I have not gotten a Chinese version of the Raspberry Pi yet, I hear there are problems with compatibility with it. You need to look at the Raspberry Pi's CPU and see if it is either a Samsung (in UK Version) or Hynix chip (in most Chinese Version). Though both chips are supposed to be identical, apparently they are not. Because of this, you need to use the latest version of the OS to insure that your Raspberry Pi will work. See: http://www.raspberrypi.org/public-service-announcement/
 
2)
I have noticed that my older Model B Raspberry Pi's tend to be more sensitive to power fluctuations and surges than my Model B+ Raspberry Pi's. If I use an Apple USB Keyboard and Mouse, the Model B freezes as the Apple KB and Mouse tends to rob a lot of power from the Raspberry Pi.
 
In this I had to buy a PC Mini Mouse and now there is no problem, though I can see the Power LED on the Raspberry Pi flicker and fluctuate. It would be better to use a wireless Mouse and Keyboard with the Model B for this reason, as power only runs the tiny wireless controller and not to separate devices. It also frees up one of the USP Ports.
 
In the Model B+, this problem almost does not exist as it uses more power efficient chips and thus more power can be given to USB Devices.
 
More issues to be posted...
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Re: The Pi's
Reply #5 - Oct 22nd, 2014, 6:41pm  
Issues Continued - Voltage on Model B.
 
Recently I obtained another Raspberry Pi from ebay. Its former owner stated that the green light would flash and not boot. I read that this might be problems with the SD Card holder, so I ordered a couple of those as well to fix the Raspberry Pi.
 
So I tried it, it would not boot. The green LED turn on and stays on, but the red LED flashes. According to the pattern of flashes, it could mean file corruption or file(s) missing from the SD. But at least it turns on and flashes. With a multimeter I checked out traces and connections and they were fine. But then I checked for voltage, it failed. Putting the multi-meter on 10 volts, I measured across T1 and T2 to get a voltage (see pics) and I got 3.25 volts. The normal is supposed to be between 4.75 volts and 5.25 volts. I did a few check and then turned on the Raspberry Pi. It eventually turned on and booted with a low voltage. I then connected it to my monitor with the HDMI adapter, and it failed - back to that flashing red LED.
 


 
I thought about it for a while. I'm using an USB extension cable on top of the tiny 3ft USB cable with the micro connector to make it reach to my monitor cable. Also, the HDMI adapter steals power in order to do the conversion to VGA. So I managed to shift a few things around to get the cable to reach, barely. It manages to turn on and boot. But plugging in an Apple Mouse got me a dead mouse. Plugging in a small PC Mouse I bought for the PIs, it works. Measuring the voltage across T1 and T2 gave me 4.5 volts, just failing but just barely.
 

 
This Model B works, despite what the person who sold it to me said on ebay. It's that it is sensitive to under voltage. Once the voltage goes under 4.5 volts, there is problems. I also noticed that it gets hot, a sign of under voltage/amperage. The Model B needs a steady 5 volts at 1 amp minimum. But over voltage or over amperage would damage the Raspberry Pi.
 
I'll continue on seeking a solution to this problem though the solution is to have a rock-stable power supply and proper wiring. Thin USB Cables can cause problems as it can limit the flow (amperage) to the Raspberry Pi from the Powersupply.
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Re: The Pi's
Reply #6 - Oct 27th, 2014, 2:04pm  
From what I can tell, the Raspberry Model A is the exact same board as the Model B.

 
The only differences between the two are:
 
Comparisons:Model AModel B
ChipBroadcom BCM2835 SoC full HD multimedia applications processorBroadcom BCM2835 SoC full HD multimedia applications processor
CPU700 MHz Low Power ARM1176JZ-F Applications Processor700 MHz Low Power ARM1176JZ-F Applications Processor
GPUDual Core VideoCore IV
Multimedia Co-Processor		Dual Core VideoCore IV
Multimedia Co-Processor
Memory256MB SDRAM512MB SDRAM
EthernetNoneonboard 10/100 Ethernet RJ45 jack
USB 2.0Single USB ConnectorDual USB Connector
Video OutputHDMI (rev 1.3 & 1.4) Composite RCA
(PAL and NTSC)		HDMI (rev 1.3 & 1.4) Composite RCA (PAL and NTSC)
Audio Output3.5mm jack, HDMI3.5mm jack, HDMI
Onboard StorageSD, MMC, SDIO card slotSD, MMC, SDIO card slot
Operating SystemLinuxLinux
Dimensions8.6cm x 5.4cm x 1.5cm8.6cm x 5.4cm x 1.7cm

 
With the missing USB/Ethernet chip and associated resistors and capacitors, it leaves the SoC-CPU to do all the work. The Model A also uses less power than the Model B, even though they share the same board. Further more, one can not just add ports to make the Model A into a Model B, you would still need to add the I/O Chip and the resistors and capacitors. You may also need to get the SoC CPU with 512MB of SRAM and replace the SoC-CPU with the 256MB of RAM. Other than those differences, they are the same. But it is those differences add up. It also brings up a few system quirks on the Model B. (See YouTube Link for demonstration of one such quirk: http://www.youtube.com/watch?v=oaf_zQcrg7g )
 
Lacking Ethernet, the Model A can still have Wifi Ethernet access through the USB Port. But since it has one USB Port, you need to use a USB or Powered USB Port on the Model A.
 
But this does not limit the Model A in what it can do, as it would be great for stand-alone applications. Automated Robotics, stand-alone sensor monitoring, and system emulation without Internet access are just a few things that the Model A can do.
 
Because the Model A has USB and Ethernet missing, it is less expensive than the Model B; $25 compared to $35 respectfully.
 
 
 
 
 
 
 
 
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Hondo I. Sackett
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Re: The Pi's
Reply #7 - Nov 22nd, 2014, 8:29pm  
This answers a question I asked in a different post. Thanks for the info!
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Well the cowboy, like the red man, you had to leave your land
You can't raise your stock and plant your crop in the gumbo and the sand
Greed disguised as progress has put us to the test
They won't be glad until we're gone from our home out in the west
It's sad to see those good old days replaced with greed and doubt
Soon we'll leave the country, the campfire has gone out
Bid 'em all adieu, you can't turn the world about
The cowboy left the country, the campfire has gone out
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