Tuesday, 27 December 2016

Thoughts on the ESP-Live

I received the raw PCB's and some of the components for the ESP-Live I wrote about a few weeks back. I have built the first prototype and I have some thoughts and ideas that I wanted to share, as well as a few photos!

Here's the GitHub link: https://github.com/ManCaveMade/ESP-Live

The ESP-Live without mains PSU module showing the Quark One in the background. The Quark One is used for power and USB to serial.

The underside of the ESP-Live. Note that I have not soldered the CH340 yet.

I have not yet ordered the CH340G USB-UART converter chips. It seem that one can only get these direct from China, which is a bit of a hassle with shipping. :( For the moment, I have simply connected the RX, TX, RST and GPIO0 pins to one of my Quark One's and I am using the bootloader on the Quark One to program the ESP-12F module.

While playing around with this setup, I think that I will not bother with the CH340's and do a fresh design... The CH340's are really cheap compared to FT232's, but I think that for a little bit more money it's worth using a proper microcontroller with USB instead - much like my original Quark One.

Why use a microcontroller, you ask?

By using a cheap microcontroller that has USB, I can achieve the same functionality as a USB to UART converter, plus much, much more to make up for the down-sides of the ESP chip:

  • Superior (and several) Analog to Digital converters
  • DAC's
  • Many PWM pins
  • Lots of timers (real-time, so it's suitable for light dimming, etc.)
  • ...
Of course, I want the ESP to be the main processor in the system as opposed to the Quark One (where the ESP was meant to be a simple WiFi peripheral). I think that it's better to use a microcontroller with a serial or SPI interface to the ESP, and then define a simple protocol to access the various peripherals from the ESP code. 

I think that this makes more sense. The ESP will be running a web server, RESTful server / client, user interface, logic, etc. and as such, the ESP could simply delegate IO to it's own peripherals and the slave micro. The slave micro needs good firmware to be written once, after which it should Just Work™.

The ESP-12F can be programmed directly from the Arduino IDE as a generic ESP8266 module!
Finally, I have some ideas to improve the electronics of v1.0 of the ESP-Live. There is a lot of unused PCB real-estatue under the PSU module. Of course, some of that space is important as there should be clearance between the mains and the rest of the low voltage circuitry. There is 2 or 3 cm of usable space, though!

I want to design a solar battery charger circuit and place it here. That way, I can use the ESP-Live with mains, and just leave the parts unsoldered. However, if I want a WiFi board out in the wild (like my garden), I can leave the PSU module off, and solder the solar circuitry!

I also want to use a smaller screw terminal without the gap (I still need to check if clearance will be ok), and then put a place for a MOV after the fuse for rudimentary protection from power surges. In case you didn't know, it's a Bad Idea™ to put a MOV before a fuse because if it fails short-circuit you want to cut the power before it bursts into flame! The house circuit breaker might do the trick here, but 15A through the MOV is not going to be pretty, regardless.

More money spending... ;)

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