Just in case you haven’t seen it elsewhere already, the good news for ESP aficionados today is that Olimex have announced an ESP32-based (WROOM-32) development board with a couple of novel features.
The most obvious is that prominent ethernet connector. According to the specs it’s a “fast” ethernet port, so 10/100Mbs. The two relays are rated at 10A/250V and it’s worth noting that, from the photograph of the bottom of the board, both the N/O (normally open) and N/C (normally closed) contacts are broken out to the screw terminals.
What makes that more useful than N/O only? Well with two relays, you now have complete control over a switched device and the existing wall switch still works as normal if your ESP32 board is powered off:-
- The N/C relay is in series with the existing wall switch and the N/O relay is in parallel.
- If the light is switched on at the wall switch, you can switch it off remotely by activating the N/C relay to open the series contacts.
- If the light is off at the wall switch, you can activate the N/O relay to close the parallel contacts, switching the light on.
- Fail-safe operation. If the power to the ESP32 board fails, your wall switch still works as normal.
- If the light isn’t being controlled by the ESP32 board, the relays are both off, so the relays don’t draw current and your wall switch, as above, still works normally.
This isn’t by any means novel, but a lot of the low-cost ESP relay control boards out there only have a single, normally-open relay contact pair available.
Moving on from the relays, there is also a micro-SD card slot available for on-board storage, two buttons, a decently sized barrel connector for an external +5V supply and a connector for a LiPo battery, with an on-board charger and step-up converter to enable battery powered operation.
There’s a 40-pin connector, which apparently gives access to all of the available GPIO pins (the pin map for the connector is silk-screened onto the bottom of the board) and, finally, a “UEXT” connector (the ten pin socket, next to the 40-pin connector). If you’re not familiar with the UEXT connector (and I certainly wasn’t), it turns out that it’s something which Olimex developed, are already using on many of their boards and have made available to the community as an Open-Source (as in royalty-free) standard. It consists of 3V3 and GND power pins, TX and RX serial pins, SDA and SCL I2C pins and MISO, MOSI, SCK and SSEL SPI pins. Now before you get too excited and start pulling all of those 30-year-old floppy disk cables out of your junk box, you should note that there’s no special magic used here; the I2C and SPI busses are still basically short-haul, on-board interconnects and you won’t be connecting remote devices over miles of (ancient) ribbon cable. On the other hand, it is quite a neat idea to be able to plug (for instance) an LCD display directly onto the board. You can check Olimex’s UEXT documentation for a (surprisingly long) list of their boards which already have this connector built in.
Unfortunately, although they’ve announced the price, at €22, the board isn’t actually available for sale quite yet. According to the Olimex blog, the prototypes are in and as soon as they’ve been tested and some example code has been written, it’ll be going into full production.
Thanks to CNXSoft for breaking the news on this one.