Today on the hookup we’re going to take a look at the new revision of the sonoff basic, figure out if it’s still useful and talk a little bit about circuit board design.
This is an old sonoff basic, the one that you’ve probably seen in countless youtube videos, but if you purchased your sonoff within the last 2 months, you probably received this, the Sonoff RF r2 power V1.0. Today we’re going to figure out how to use this new version of the sonoff basic, and talk a little bit about why itead may have made this revision.
First lets talk about what hasn’t changed: In the middle of the board you still have all of the pin holes that you need to flash your device with custom firmware, RX, TX, Ground and 3.3V. GPIO-0 is still tied to the push button, so you can just hold it down during power on to enter flash mode, and in that sense the process of flashing your sonoff hasn’t really changed at all.
But if you’re looking to do anything more advanced with your sonoff, you’ll quickly notice that instead of 5 pin holes like the old sonoff basic, the new version only has four. That’s because GPIO14 is no longer broken out. Instead, people have been setting up their external devices using the solder pad labeled “Key”, which corresponds to GPIO2. In this video, I’m going to advise against that, since GPIO2 is one of the most troublesome pins on the ESP8266.
Last summer I made a video about the quirks of the GPIO pins on the ESP8266, and as you can see, GPIO2 has two problems: First, the pin goes high during the boot process, so if you have a device that turns on/off when voltage is applied, it will kick on for about 400 milliseconds when your sonoff reboots. Second, you can see that if that pin is pulled low on boot (meaning it is attached to ground), the ESP8266 will go into one of it’s alternate boot modes, which won’t run the main program on your sonoff, and will therefore result in a non-working device.
The fix for this is pretty simple. We know the other two pins that are available to us are TX and RX, and you can see on my diagram that TX corresponds to GPIO1 and RX corresponds to GPIO3. Both of these pins are also high on boot, which is unfortunate, but you can see that GPIO3 won’t cause boot failure when pulled low. That means that the best option for hooking up an external switch or sensor is going to be GPIO3, the RX pin. The only downside is that the serial connection isn’t going to work anymore in this configuration, but you won’t need that after you’ve flashed your sonoff anyways.
If you run into any other issues using the new version of the sonoff basic, post them down in the comments and I’ll try to help you out. If you’re interested in the reasons itead made this revision, keep on watching.
Sonoff seemed to be a pretty good product at an impossible price before, so why did itead do a complete board revision? Some possible motivations could be: electrical certificate compliance, cheaper production costs, discouraging hacking and modification, and maybe just safety for safety’s sake.
I don’t work for Itead, so I can’t be sure of the exact reason, but there’s no doubt in my mind that the Sonoff RF r2 power is a more thoughtfully designed circuit board than the original sonoff basic.
The most obvious change is the shift from using circuit board traces to wires for carrying mains voltage from the relay to the terminal. Most people don’t put enough load on their sonoff basics to cause and overcurrent situation, but the length of the traces on the basic were unusually long for carrying mains voltage and to alleviate this issue Itead used to add extra solder to these traces to decrease their resistance. The problem using globs of solder is that they aren’t always a uniform thickness and that can lead to hotspots on the trace that can ultimately lead to failure.
The wires on the new r2 version of the sonoff basic are a far better solution for carrying current, but they also have the added benefit of increasing the separation between high and low voltage, which is another place that this board shows thoughtful redesign. On the old sonoff basic there was separation between AC mains voltage and DC voltage, but the rectified high voltage DC passed pretty close to the low voltage area. I’ve never had a problem with my old sonoff basics, but it would be theoretically possible for a surge of power to cause an arc between the traces in these areas sending high voltage to the low voltage outputs.
It’s possible that itead did this redesign to comply with a specific certification agency, but it would likely still fail most major safety certifications due to the fact that the sonoff basic is intended to be used where the end user is likely come in direct contact with it. There’s even a button on top for the end user to interact with. By having this button itead adds a slew of extra safety requirements related to voltage division and also grounding, which the sonoff basic famously lacks.
Another major upside to the new redesign is the fact that the ESP chip, which is actually and ESP8285 instead of an ESP8266, on a huge ground plane with a bunch of small holes called via’s punched in it to connect the top ground plane to the bottom one. This helps significantly with heat dissipation and should allow the ESP chip to run a bit cooler than on the previous sonoff basic.
Using the ESP8285 also saves itead a few cents per unit, since it has 1 megabyte of built in flash memory, rather than having to include an external flash chip like the previous sonoff basic.
The last thing, and the thing that I just can’t seem to understand at all, is why they chose to breakout GPIO2 instead of any of the other pins that don’t have boot problems. Part of me is wondering if it was to discourage modification of their devices. That would be a bummer since the DIY community is largely responsible for the success of the sonoff basic in the first place, but also understandable since every picture I’ve ever seen of a melted sonoff was the result of improper modification or blatant misuse.
If I missed any obvious changes to this board, let me know down in the comments section. If you found this video helpful give it a thumbs up so youtube will suggest it to other makers and DIYers.
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If you’d like to pick up one of these new sonoff basics, I can confirm that the amazon listing that I have in the description is shipping the new version only. If you enjoyed this video, please consider subscribing, and as always, thanks for watching the hookup.