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Eben Upton Explains the Raspberry Pi Model A+'s Redesign
M-Saunders writes It's cheaper, it's smaller, and it's curvier: the new Raspberry Pi Model A+ is quite a change from its predecessor. But with Model Bs selling more in a month than Model As have done in the lifetime of the Pi, what's the point in releasing a new model? Eben Upton, a founder of the Raspberry Pi Foundation, explains all. "It gives people a really low-cost way to come and play with Linux and it gives people a low-cost way to get a Raspberry Pi. We still think most people are still going to buy B+s, but it gives people a way to come and join in for the cost of 4 Starbucks coffees."
Given the purpose of these devices, cheaper would be better than faster.
The A+ and B+ boards still have composite video, they just output it on the smaller 3.5mm jack to save space, like many other mobile devices do. You can get adapter cables to split out the typical red,white,yellow RCA connectors for a couple bucks.
For most tasks, it has more than enough power. The pi isn't for people looking to use it as a PC replacement for productivity. It is a low cost board. The reason the RAM is always fixed at 512MB is because the cheap SoC (system on chip) is a PoP (package on package) design. Inside the chip you see on the Pi lives both the SoC and the RAM. There is no external memory bus so it is impossible to upgrade the RAM without redesigning the silicon and retooling an entire production line. That isn't going to happen because Broadcom isn't interested in upgrading an outdated (which is why it is cheap) chip.
It's best use is an embedded controller that runs Linux. I have used one for a little home brew project and it works perfect. You don't need 700MHz for a control loop to turn relays on and off. But it does come in handy when you want to make a web based controller. I installed node.js and the cloud 9 IDE like the Beaglebone and I had a web page controlling relays in a matter of a few hours. Sure you can make a web based controller in a much smaller device like the Mbed but having Linux makes it much easier as you have a familiar development environment and tools. And you can write the software right on the Pi itself, no need for cross compilers, tool chains or a separate PC. Just a keyboard, mouse and monitor.
While the Pi is good for most of its intended tasks, it is lacking in many areas. The Beaglebone is a good upgrade but it too has shortcomings. But if you need more power, the Beagle team has another board in the pipeline.
If you want some serious power for an embedded project look no further than the Beagleboard X15. This thing is going to be a beast:
Dual core A15 ARM @ 1.5GHz
2GB DDR3L RAM
Dual core GPU (unfortunately PowerVR SGX, not open source friendly)
2D accelerator and Video accelerator
Dual C66x DSP processors
Dual Cortex M4 Image processors (only one is user programmable)
Dual PRU-ICSS ( programmable cpu accelerator to offload ethernet packet processing for industrial protocols like Ethercat, Profinet, etc.)
eSATA
USB 2.0 and 3.0
Dual PCIe ports, Gen 2, one x1 and one x2 (Yes they will be routed to ports)
Appears to have some type of video in, probably a camera port.
And more...
Rumored to cost about $150. Yes it costs much more than the Pi but you get what you pay for; a boat load of processing power and memory.
You forgot to include "at a similar price point." Because, despite all the hoopla about its other features, that is the biggest selling point of the RPi: it's easy to replace a fried unit after a voltage calculation mis-places a decimal point.
> I drive relay boards
> We have three here already, and I'm probably about to add a fourth.
If you need to drive a lot of relays, you might consider a serial-to-parallel chip feeding a ULN2803 octal darlington array. That's about $2.50 of electronics per eight relays. With connectors and such, call it $0.50-$1 per relay. You can connect up to 256 addressable serial-to-parallel chips to a single IO on one Pi (or a PC, through a $2 level shifter). So for the price of another Pi, you can add 35-70 more relay outputs to your existing Pi.
The Model A boards have 256MB, the Model B have 512MB. They could have put 512MB in the Model A, but it would have cost them a bit more and they were trying to make it cheaper. (I still wish they'd done it.)
But one reason the board is so cheap is that it's using a System On A Chip that's designed for other applications, not custom for them, so making it faster, or using a newer ARM instruction set, or (apparently) putting more than 512MB on the board would be hard, requiring a major redesign and increasing costs. For instance, the BeagleBone Black costs about twice as much, and while it uses a faster CPU with a newer instruction set, the video processing part is slower, so it's not a total win.
Bill Stewart
New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks