I got two of these for a projects which need a large flash memory. link (https://www.ebay.com/itm/CP2104-ESP12F-USB-16MB-Wifi-WeMos-D1-Mini-Pro-NodeMcu-ESP8266-ESP-8266EX/201929770302)
I have already noticed two odd things:
1. The resistor divider circuit at board pin A0 is a 100K : 10K. Since the ADC on the ESP12F module is designed for max 1 volt, this would appear to mean that 11 volts on A0 would yield the maximum analog value of 1023.
2. The position of the reset button is rather odd, on what appears to be the underside of the board. I don't use the wemos shield system so I have mounted one upside down to keep the button accessible.
Is there a special concept with these boards or are these errors ?
No idea about the voltage divider.
The reset button is not at the underside of the board. But the manufacturer might have soldered the pins at the wrong side for 'normal' use. The way it is now you can mount the Wemos in a case with some stand-offs and easily stick dupont cables on it. I think that you should have checked before buying ;)
. . . I think that you should have checked before buying ;)
Thank you for that. I will treasure your invaluable advice.
For me it is no problem and I have chosen to in such a way as to give access to the button and am already using one for my application, but since wemos shields exist, there must be a correct orientation and maybe someone else benefits from this discussion. That with the issue of the A0 voltage divider indicates that the design may not be very mature.
That with the issue of the A0 voltage divider indicates that the design may not be very mature.
Or just cheap chines crap (another advise to treasure :) ). The (official) D1 mini schematic (https://wiki.wemos.cc/_media/products:d1:sch_d1_mini_v3.0.0.pdf) indicates 220k/100k.
Yes, your schematic shows the "standard" nodeMCU type 220K : 100K divider that gives analog value of 1023 with 3.3 volt. I guess the manufacturer had a either a shortage of 220K resistors or a surplus of 10K resistors. It runs very warm also (regulator and schottky diode) so I'll check at sometime if other components substitutions have been made. Anyway, the stuff is so cheap that I can just throw it away in, the worst case, and try something else. The 2 to 3 week delivery time is miserable though.
This gets worse. Now I have attempted to use these in a project where a full 16MB flash ESP8266 is required. They worked OK when treated as a 4MB version but always failed during the SPIFFS.begin() when attempting to use 16MB. After a lot of playing around including updating to latest Arduino ESP8266 core, creating a minimal test sketch etc. etc. I discovered, by removing the soldered on cover, that these are not 16MB as claimed. They are only 4M.
Maybe this spares someone else wasting a lot of time.
1. The supplier of the "Wemos 16MB" clone gave me a refund (almost all that I asked).
2. I've ordered 2 of these which appear from the description to be genuine, better specified and cheaper than the clones (but without free delivery). Lesson learned.