The Raspberry Pi 3 Model A+, the unknown entity

Recently, I had a very interesting "aha" moment while developing the new control for drop photography. Maybe it was only new for me, but in case it is not, I still want to report about it briefly.

In the past years I have done some more or less big projects with a Raspberry Pi. The decision which model to use was always very easy. The Raspberry Pi 4 is very powerful, but completely oversized for my needs. And since I don't want to use any old hardware, apart from the Raspberry Pi Zero W, only the Raspberry Pi 3 Model B+ remains. At least that's what I thought.

Der Raspberry PI 3 A+

While searching for info about the Raspberry Pi Touch Display, I eventually landed on the Raspberry website. While scrolling through the products, I noticed the Raspberry Pi 3 Model A+. I could not believe my eyes. This is exactly what I need. I almost always disable the USB/LAN chip and also the HDMI output, because I only need the WLAN and the GPIO ports. Why I don't use the Raspberry Pi Zero W or even an Arduino, I will explain in a moment. Before that, a small overview to clarify the differences between the models:

  Arduino Uno Zero W 3 Mod. A+ 3 Mod. B+
 Length 68,6 mm 65,0 mm 65,0 mm 85,6 mm
 Width 53,3 mm 30,0 mm 56,0 mm 56,0 mm
 Height 12,5 mm 5,0 mm 12,0 mm 20,0 mm
 CPU ATmega328P (8 Bit) ARMv6 (32 Bit) Armv8 (64 Bit) Armv8 (64 Bit)
 Cores 1 1 4 4
 Clock 16 MHz 1000 MHz 1400 MHz 1400 MHz
 RAM 32 KB Flash + 2 KB SRAM 512 MB 512 MB 1024 MB
 Ethernet - - - 10/100/1000 MBit/s
 WLAN - 2,4 GHz b/g/n 2,4 u. 5 GHz ac 2,4 u. 5 GHz ac
 Power 0.29 W 0,5–0,7 W max. 4,24 W max. 7 W
 USB 2.0 1 1 OTG 1 4
 Interfaces GPIO (14 Digital, 6 Analog), SPI, ICSP, I²C GPIO (26 Digital), CSII²C GPIO (26 Digital), CSIDSI, I²C GPIO (26 Digital), CSIDSI, I²C
 Price 22 Euro 12 Euro 25 Euro 38 Euro

The suitable hardware depends, of course, on the respective requirements. For the drop controller, for example, the following criteria were important:

  • Programmable in a high-level language (Python, Java)
  • DSI interface
  • Low power consumption
  • Cost
  • WLAN, ideally 5 GHz
  • Low space requirement

In the table above, the values that most closely meet the criteria are marked in color. And as you can see, the Raspberry Pi 3 Model A+ meets all of them. And in my other projects, the criteria were quite similar. I just can't believe that so many hobbyists need the Ethernet and all 4 USB ports. But as I said, of course the requirements depend on the project. Still, it's a mystery to me why the Pi 3 Model A+ is so unknown. A good example is the image search on Google. The search term Raspberry returns almost exclusively the B+ models. Even otherwise, I haven't come across any project that uses the Raspberry Pi 3 Model A+. And that, although it has been available for purchase since the end of 2018.

In any case, I will only use the Pi 3 Model A+ in the future, as long as my requirements do not change. It is a cheap and space-saving alternative to the Raspberry Pi 3 Model B+, if you can live without Ethernet and get by with one USB 2.0 port.

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