Raspberry pi boards comparison

In a previous post, I explained the most recent model of raspberry pi board, the 3B+ board, and my take on why you want a raspberry pi. This post is about comparing the different models. Again, if you are taking on the raspberry pi hobby, get the 3B+ with quad-core 1.4GHz processor, 1GB memory, and most recent Wi-Fi/Bluetooth on board. It’s easy and fun to use. Other boards are made for specific reasons or tasks.

The following is the most popular one of all, the model 3B+:

Next, let’s see the most recent model, the model 3A+:

If you compare them side by side, you’ll notice that 3A+ is almost the same as the 3A+ except it is missing the stuff on top of the photo:

Here is zero W. It is only about a third of the size of the 3B+ or half the size of the 3A+:

How do these boards compare?

A VS. B VS. Zero

There are three models of raspberry pi boards at the time of this post A, B, and Zero. Please don’t attempt to buy the Compute modules. They are out of the general discussion and only are relevant to circuit designers with enough skill levels to integrate into their products.

Originally there were only two models, the model A, the cheaper with less features and the model B, the full-feature one. There are three generations of them already, gen 1, 2, and 3. Major improvements were made between generations, such as doubling memory and using a quad-core in gen 2 or adding wifi/BT in gen 3. When they make smaller improvements to their designs, such as using a faster processor or better Wi-Fi module, they will put a “+” after the model, such as 3B is superseded by 3B+ with faster processor, faster ethernet, more recent Wi-Fi and Bluetooth connectivity, and more power-hungry than ever.

The model B boards are the main stream boards. The model A boards have less memory, single USB port and no Ethernet, and at times not offered to contrast every model B offering. They have always kept the $35 price tag for B and less for A, such as $20 or $25. The intent of model A is to have it run a project that doesn’t need all the USB ports or Ethernet. Say you want to run some slides on a big screen, you don’t really need more than just the processor and sd card. USB ports or Ethernet are optional. You can save money with model A. Last time I visited Minnesota Institute of Art, I took a peak behind their big screens. They were mostly using model B (probably gen 2 or gen 3, not the plus with metal heat sinks)! I couldn’t take a photo or investigate more though. It’s an art museum any. People go there to see art, not raspberry pi?! Anyway, that would be a use case for model A.

Now (in 2015) the raspberry pi folks wanted to challenge themselves to come up with a computer as cheap as $5 (again accessories count as extra), possibly because many other folks started spinning their own boards with similar specs to raspberry pi and many advertised for low prices. So they did it with model Zero, cramming all that raspberry pi goodness on a board only a third the size of a regular pi. Apparently it is not a prequel to gen 1. They slapped the same processor their gen 1 was using and did away with USB or Ethernet, resulting in a much smaller (only on the look) board that they are selling for $5. Is it really that cheap? I’ll never know. They only sell you limited quantities, such as 1 per customer.

Apparently their successfully answered the challenge to themselves and the community was clamoring about it. They designed a sequel, the Zero-W, with a Wi-Fi/BT on board, same as the Wi-F-/BT on their 3B+, for $10 each. This is better than the Zero, since you can’t really interact with the Zero easily. You first need a mini-HDMI to HDMI adapter to bring out the video. Then you need a USB-otg adapter to hook up a keyboard/mouse combo. If you have the Zero, you have no network! You can install nothing or update nothing. You need to get a USB hub and a USB-Ethernet dongle, for another $10 or more. This newer model is again on limited stock. You can buy more than one if you wish to pay a premium of $15 each, or $20 each if you wish to get more than half a dozen. Definitely these Zero models are NOT for any practical projects that need to be deployed at more than a few locations.

Performance

If you wish to use a raspberry pi as a desktop computer, definitely go with 3B+. 1A and 1B are both obsolete, having single-core sub GHz processors. My oldest raspberry pi is a 1B. It’s painfully slow as a general-purpose computer. I was disappointed at it since the original goal of this device is to teach kids computing. The two mounting holes that were haphazardly placed on the board like an afterthought also bothered me. I did a few projects on it. But nowadays it is sitting idling in its case, inside my box of raspberry pi stuff. In 2014, they cleaned up the board and pushed out 1B+. It’s much easier on the look, and to use, since it comes with 4 USB ports and 4 symmetric mounting holes. This footprint has become the standard for the rest of their models A and B boards. The mounting holes and connectors would be at the same location across multiple generations, and they don’t plan to change. Same processor is used on the model Zero series so far, with a single-core processor now overclocked to 1GHz and 512 MB ram. I do use one of them, the one without Wi-Fi, as a data logger. I had to tether all the wires, USB-otg, to a USB hub, then a USB-Ethernet dongle and a sensor on USB. But since it’s sitting in my garage headless (no keyboard or monitor), I don’t need HDMI or keyboards. I could use the Zero W but still have to have the same stuff due to the sensor on a USB port. Gen 2 only has 2B, no 2A. It’s obsolete as well although you can still buy them. They are better in desktop performance already but would require Wi-Fi dongle to connect to home network. I used to tether my 2B to an Ethernet port on my home Wi-Fi router. Now it’s sitting inside another box with a preloaded program that I might run as a demo. 3B gives you pretty decent desktop performance, comparable to a netbook with Atom processors. I got a retropie running on it, emulating old video game consoles. It has no problem running those emulations. The 3B+ is pretty nice. I use it when I need to get some work done on it. I now have a 3A+, which sports the same processor as the 3B+, with half the memory. It runs fine. I just want one for my small collection and in case I need it for something (probably never, other than blogging about it).

Projects

There are some projects that you need the smaller footprints and you don’t mind soldering/desoldering, you go with ZeroW. Performance is low, as space is premium for your project. You can add more USB ports with custom extension boards but the size and price both go up. You can connect a camera to it too. If you rely on adapter wires to get to the USB port for instance, then your project size will likely double due to the difficulty of bending that adapter to fit in place. Trust me, trying to organize cables with “huge” connectors such as Micro-USB is no fun.

If your project is not limited by size as much, but doesn’t benefit from having more than one USB port, such as a big TV slide show/display case/kiosk, and you potentially want to deploy a number of them, go with model A (3A+). You don’t need the added USB port, Ethernet, or double memory for those tasks.

If you want more flexibility for your project, go with the model B (3B+). You won’t be disappointed. There is a chance you can trim down the requirements into 3A+ in case you deploy your project in many locations.

Note: all photo credits to raspberrypi.org or myself 🙂

Raspberry Pi 3A+ vs. 3B+ and all those other models

This post is intended for those that are considering starting their journeys with raspberry pis or just want to know a bit more about what raspberry pi boards offer which features. If you are a raspberry pi history buff, or raspberry pi advocate (me too but for different reasons than yours), read on as well. Leave me some comments! Not only are specifications of raspberry pi board explained, but also my take on the question “why you want a raspberry pi”. If you wish to know more about the differences between different raspberry pi boards, read my next post.

The raspberry pi folks have released another version of raspberry pi, this time, the 3A+ version. I grabbed one right away when my local electronics store got these boards in stock. While I was browsing accessories (believe me you can never have enough raspberry pi accessories), trying to find the official white/raspberry 2-color case, I overhead a couple of people talking about raspberry pi. They were just reading off the labels and that was already confusing enough for them, 3B, 3A+, 3B+, zero-W etc. I know from their voices that they were not being sarcastic, just genuinely confused what’s what. They walked away before I could strike a conversation with them. I thought, if you are just starting with raspberry pi, then what are all these designations and more importantly which board should you get?

The second question is simple, beginners should get the best model, the 3B+ model with the fastest processor + most memory + most USB ports etc. The prices only differ as little as $10. The cheaper ones are meant for more specific applications.

What you get for a rapsberry pi 3B+ is the following features for $35 (extra for required accessories I’ll talk about later). Every feature has my comments for beginners:

Raspberry Pi 3B+:

  • Quad-core 1.4GHz processor: This is a fairly decent processor not too different from the processor of a netbook around $200 (Broadcom BCM2837B0, Cortex-A53 (ARMv8) if you want the details)
  • 1GB memory: This is not a huge amount of memory but the Linux OS is not a memory hog that windows is. (LPDDR2 SDRAM to be exact)
  • Most recent version of Wi-Fi and Bluetooth: you can connect to your home Wi-Fi in seconds although Bluetooth connection can be a struggle just because Bluetooth itself is such a struggle to use (2.4GHz and 5GHz IEEE 802.11.b/g/n/ac wireless LAN, Bluetooth 4.2, BLE if you want to know)
  • Ethernet: connect to your router with a CAT-6 cable for network if you don’t want to use Wi-Fi (Gigabit Ethernet over USB 2.0 (maximum throughput 300 Mbps) to be exact)
  • Extended 40-pin GPIO header: for tinkering with electronics, such as blinking an LED or controlling motors to your custom robot (most accessories sold for raspberry pi are compatible with this pin layout)
  • Full-size HDMI: this is nice so no adapters needed, just straight HDMI cable
  • 4 USB 2.0 ports: minimally you need a keyboard-mouse combo dongle, maybe a flash drive and other devices such as a gamepad, or Arduino etc.
  • CSI camera port for connecting a Raspberry Pi camera: this connects to a camera with special interface for future projects. The camera, which is a $25 separate official accessory, comes with no enclosure or mount. You need an enclosure or separate stand to make it useful. It is also a nice thing since you can make your own design where the camera goes on your own enclosure.
  • DSI display port for connecting a Raspberry Pi touchscreen display: this connects to an official display with special interface for future projects. The display is rather expensive at $60 and needs some assembly. Again it comes without a stand, just the display and an exposed driver board. You need to buy a stand or make your own so the pro of flexibility and con of not a complete solution.
  • 4-pole stereo output and composite video port: probably not useful for most people and projects unless you want your old TVs for display.
  • Micro SD port for loading your operating system and storing data: you need a MicroSD card at least 16GB since raspberry pi has no storage, costing you extra $10.
  • 5V/2.5A DC power input: this is just a MicroUSB socket. You need a USB-to-Micro USB cable (aka Android charging cable) and a phone charger. The required power is rather high so you can’t use your old Android phone charger. I have a couple of generic AmazonBasics chargers with 2A current. Make sure you get a short fast charging cable with thick conductors. Those generic Micro-USB cables have very thin wires that drop too much voltage on themselves so what they deliver to your raspberry pi is often insufficient, causing all sorts of problems.
  • Power-over-Ethernet (PoE) support (requires separate PoE HAT): probably not a beginner’s feature. With the official accessory (a HAT), you can deliver both internet and power through a single CAT-6 cable to your raspberry pi, de-cluttering cables by a great degree. The accessory is “expensive” considering it is $20 extra dollars just to get rid off the Micro-USB charging cable. That’s not the end of it. The other side of the CAT-6 cable, the router, needs to support PoE and has PoE injector. The HAT also covers all your 40-pin headers, so no more tinkering with electronics.

So let’s see, you get a netbook-level computer for $35. Add the following accessories that you may already have:

  • $10 for 16GB+ MicroSD card
  • $10 for USB charger
  • $5 for charging cable
  • $20 for the cheapest keyboard and mouse combo
  • $5 cheap HDMI cable
  • $5 cheap case (official version is $9)

This isn’t everything. If you don’t have a monitor, that’s extra $$$. So the minimal equipment cost is $35. A realistic cost is maybe $75. If you want to set up everything from scratch, it’s $100 plus whatever the cost of a monitor. By this time, you should realize that buying a raspberry pi is not going to save you much money from buying a new PC. A PC laptop with the same if not better spec can be bought for less than $200. You can take said laptop anywhere you want and use it for hours between charges. Raspberry pi can’t do any of that! There are kits you can buy and assemble yourself to make a raspberry pi into a clumsy laptop if you wish to dish out $300+.

So apparently a raspberry pi is NOT a cheap PC replacement! You will NOT save money buy purchasing a raspberry pi! Should you still get it? If you’re deciding between a cheap computer for school and rent, you should just go with a cheap computer. If you have $100 extra money you saved up for “new cool tech things”, you should buy a raspberry pi. That’s right! Raspberry pi is a HOBBY! I don’t remember having hobbies when I was poor. That’s OK. Unless you’re really struggling to support a family, you can find money for this one hobby. Raspberry pi is not an expensive hobby. If you are interested in technology, this hobby will pay you back in many ways that exceed your already-moderate and low-risk investment. Delay that “smart phone” upgrade! All of a sudden, you have extra money! Make yourself sandwiches or some real food, use a few coupons at supermarkets, bring fruit and soda to work/school, come early and find free on-street parking.

Anyway, the real “specs” that I would like to say, are not measured in Gigabytes or GigaHertz. They are measured in more qualitative and subtle things:

  • Take a journey in popular computing technology, with millions of stops depending on what your interests are
  • Become a maker and have computers, sensors, motors, the internet do things for you, not just what you can buy from the stores
  • Be part of an extremely creative global maker community with people from all walks of life with all backgrounds that all share the love for computers and innovation

 

Can’t upgrade pyserial in latest raspbian distribution?

This is just for your information if you are a Raspberry Pi user and playing with Python code from my blog. If you are trying to use the latest distro of raspbian with pyserial for some serial port project, you may have come across this issue that regardless how you upgrade pyserial using pip3, your python3 will always call up the old pyserial 2.6 that came with the distribution. I am a bit disappointed that the foundation has included such an old version of pyserial, couldn’t they just try a pyserial 3.0 instead? My solution was to remove the python3-serial module using apt-get and then install pyserial 3.3 using pip3.

sudo apt-get remove python3-serial
sudo pip3 install pyserial

Hope this helps.

Soil data logger telemetry

I have finally found time to build a simple website for my soil data logger with telemetry. The system works as the following:

  1. The data logger consists of a raspberry pi and my SDI-12 USB adapter with a Decagon 5TM soil sensor
  2. The data logger runs the open-source datalogger code I wrote in Python to first get parameters from the user (COM port, SDI-12 address, delay etc.), and then collect data, save to a local .CSV file, and then send the same data to sparkfun’s phant server.
  3. I constructed a web interface to plot the data using Google Charts and download .CSV version from sparkfun’s phant server.

Here is a screen shot:

soil logger webpage

I’ve uploaded the webpage to a server with a link below. The sensor is apparently NOT buried in soil so I can easily take the setup and set it up in different places to test its stability.

Link to the website: Link

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