There are new boards in town, and these are interesting for more than one reason. Sonoff 4CH & 4CHPRO are now available as an R3 revision. That’s not the only change, so let’s take a closer look at both boards and talk more about why Sonoff 4CH & 4CHPRO are pretty cool and why 4CHPRO is an automation beast!
Sonoff 4CH & 4CHPRO what’s new?
Both Sonoff products went through an internal and external redesign. Gone are spring-loaded terminals, replaced with screw terminals – that’s a welcome change as the old ones are a nightmare to work with. The boxes are more rounded and feature a new locking mechanism for DIN rails. These are going to be very easy to snap onto the rail.
4CH R3
Driven by ESP8285 just like the R2 revision, 4CH keeps the electrical properties and the Sonoff board is capable of switching:
- 10A max per channel
- 16A per device which equals to 4A per channel of constant load
- Not recommended for the inductive load as the rush current may damage the unit. ( The operating current should be less than 10A/Gang(40A/Total). The operating power should be less than 2200W/Gang(8800W/Total). If it is an inductive load, please confirm the rush current instead of the operating current.)
The 16A shared across 4 channels may not seem like a lot at first but that’s over 800W per device (mains here are 220V) and I’m not planning on automating my vacuum any time soon. I didn’t like how the board is powered on. Both, live and neutral wires connect to two different headers. I had to strip the wire significantly to be able to power the device on. This will apply to every device connected to the 4CH R3.
The PCB reveals that ESP8285 is now part of the mainboard. It’s a tradition for Sonoff devices to expose programming inputs. There are 5 pins exposed with a breadboard compatible header (RT, TX, GND, Vcc 3.3v and GPIO02) and there is a dev pad to RST pin too. Flashing 4CH R3 should not be an issue.
ESP8285 
Front 
Back
Further probing reveals
| # | Relay | Button |
| 1 | GPIO12 | GPIO00 |
| 2 | GPIO05 | GPIO09 |
| 3 | GPIO04 | GPIO10 |
| 4 | GPIO15 | GPIO14 |
LEDs are associated with the input pins and are drawing from the same source.
4CHPRO R3
It’s also driven by ESP8285, with unchanged electrical properties:
- 10A max per channel
- 40A per device which equals to 10A per channel of constant load
- Not recommended for the inductive load as the rush current may damage the unit ( The operating current should be less than 10A/Gang(40A/Total). The operating power should be less than 2200W/Gang(8800W/Total). If it is an inductive load, please confirm the rush current instead of the operating current.)
A quick look inside reveals a couple of hardware changes. First, physical separation of relays improves safety, ESP WiFi is embedded into the main PCB and inching and interlocking controls are removed from the board itself.
In line with other Sonoff products, PCB contains the dev header with RT TX GND Vcc exposed. There is also an SDA pin, but GPIO02 is not present. SDA suggests an I2C interface but a quick check with a multimeter confirms that the pin labelled as SDA is in fact connected to GPIO02.
ESP8285 
Front 
Back
Further probing reveals:
| # | Relay | Button |
| 1 | GPIO12 | GPIO00 |
| 2 | GPIO05 | GPIO09 |
| 3 | GPIO04 | GPIO10 |
| 4 | GPIO15 | GPIO14 |
It also looks like the LEDs associated with relays are powered by the signal from connected GPIOs. This should give you more than enough information to start hacking it.
Sonoff 4CHPRO comes with an RF433 component as well. I was able to link a Sonoff Remote directly by holding the respective buttons for a couple of seconds (until you see a pink flash). Worked perfectly. Just remember to hold the remote button for about 1 sec to activate the relay. Another way to interact with this board is to link the remote buttons to a Sonoff RF bridge (review). You can use virtual buttons as inputs. It’s a niche use, but if the relay is in a place outside of the WiFi range, you may have better luck with RF433 instead. You can link up to 4 remotes per channel (16 buttons per relay). If you need further information – this is the correct manual PDF for you.
The board features dry contacts (decoupled) in both DC and AC power modes. It’s great for connecting other than mains voltages or even using AC and DC on different relays as long as you don’t exceed suggested power ratings. While I’m speaking about DC, the min voltage requirement has changed and 4CHPRO requires min 9V DC to be operational. If you are hoping to replace the R2 series powered by a 5V supply, you will need to change the power supply as well.
Software changes
Sonoff 4CH & 4CHPRO benefit from the hardware changes. Inching and interlocking are available via software implementation, removing the arbitrary inching limit of 16 sec (max 60 min right now) and the interlocking can be enabled in the eWeLink app. You will sacrifice some timers and schedules by doing so.
Both Sonoff 4CH & 4CHPRO come with a “per-channel” power on settings, so you can customise how the relays behave after a power loss. Timers are available per channel only – I believe there is a limit of 8 active timers and schedules together with 20 in total stored in the memory.
I’m slightly confused by the R3 designation as I was under the impression that devices branded by this revision (and having DIY printed on the manual) would get DIY 2.0 mode. Unfortunately, this is not the case. In the email from ITEAD PR, I found out that there are no plans to add DIY mode to these two units for now. It’s a big disappointment as I liked where DIY 2.0 mode was heading.
The LAN mode is still present, in case your internet is spotty.
Final thoughts
It looks like this will boil down to two options. Option 1: flash Tasmota, which is what I will probably end up doing. Option 2: use eWeLink API to control Sonoff 4CH & 4CHPRO R3 from NodeRED and other services. I guess I will have another write up to do soon about it! Let me know what do you think about the new Sonoff 4CH & 4CHPRO R3 boards in this Reddit thread.
