What are the differences between an Arduino Yún and a Arduino Uno with an added Yún Shield? And is there a way to expand the storage of the Yún / Yún Shield?
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2 Answers
As Majenko wrote: the Arduino Yún = Leonardo + Yún shield. You get into a lot of trouble with the Arduino Uno, and the Yún shield has already enough troubles on its own.
Maybe the Arduino Mega 2560 can be used when both the hardware and software is changed to use another hardware serial port for the Yún shield. If you start with the Yún shield, then use the Leonardo. Don't even try the Arduino Uno.
It is possible to upload a sketch via Ethernet or WiFi, but that often fails. Therefor you need the usb-serial connection to the computer to upload a sketch.
Even when you use a Arduino Leonardo, the communication between the Yún shield and the Arduino board (the 'Bridge') can cause troubles. In OpenWRT a Python script is used to read the serial data from the 'Bridge', which causes a lot of CPU usage.
The Yún shield is not fully compatible with the Arduino Yún. I think a few GPIO pins are different and maybe some other things. That means you are stuck to the firmware of the Yún shield, which can have issues and is not fully compatible with the Arduino Yún firmware.
When installing software in OpenWRT, the rootfs is filled quickly. You can type df or df -h to see the disk usage. I have read about ways to add a SD memory card or a USB flash drive to the rootfs. I have not tried that because I want OpenWRT to run even without a SD memory or USB drive.
An SD memory or USB drive can be used to store a website on it, or scripts, or music files, and so on.
When you need more memory, you might want to try the Raspberry Pi. The Raspberry Pi Zero W is very cheap and has WiFi.
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I already own a 1x Raspberry Pi B 512MB and 2x Raspberry Pi 3, Arduino Yun interested me Commented Apr 19, 2017 at 5:13
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Using OpenWRT is fun, since everything is optimized for small systems. However, my advice is to stay away from the Yun. The 'Bridge' causes too many problems. If you want to get closer to the Arduino, the NodeMcu is better.– JotCommented Apr 19, 2017 at 17:13
The differences are manifold.
The biggest difference is that the Yun employs an ATMega32U4 as the MCU, whereas the Uno employs the ATMega328P. This has big ramifications with the Yun shield.
- The ATMega32U4 uses a dedicated USB connection to the USB socket, and a dedicated UART connection to the MIPS SoC.
- The ATMega328P has only a UART connection which is shared between the USB interface and the MIPS SoC.
This means that the Yun shield can interfere with the operation of the USB connection. You cannot communicate between the MIPS SoC and the Uno whilst at the same time using the USB connection, like you can with the full blown Yun. Uploading sketches can be an issue - you may want to remove the Yun shield while uploading.
The Yun is closer in operation to an Yun Shield + Arduino Leonardo than an Uno.
