ESP8266 Community Forum

- Tue Nov 08, 2016 4:18 pm #57849 Pardon me for belaboring this, but I am new to ESP8266/NodeMCU, and I have 3 hardware questions (some are off topic, but rather than 3 separate posts, I will just post all 3 here:

1. I need to connect Serial Out only to a display. The display runs on 5V, and is TTL serial. I would like to connect it directly to D10/TXD0 (NodeMCU/ESP-12). I have read that it is OK to do this since the 5V pullups on the Display would not ever source any current. Thoughts? I understand that this is shared with the integrated FTDI, and I will see garbage during boot and when connected to ESPlorer, but I do not care.

2. I would like to run the entire thing (Node MCU and display) from the USB connector on the NodeMCU. The display draws about 0.5A. Is the 5V from the USB connected to the NodeMCU VIN connector? It looks like the schematic shows there is a diode in there to prevent ViN from feeding back to the USB, but I would be "going the right way" through that diode. Can it handle 0.5A indefinitely?

3. (Even more off-topic, but still about pins): Does anyone know of a source of NodeMCU Dev kits sold without pins soldered in? I only need the serial out, 5V pin as mentioned, and a PCM out.
I could buy just a plain ESP8266, but by the time I make a board with USB connector and 3.3V supply, it is more convenient and cheaper to just use a NodeMCU even in "production" units (I don't actually plan on building more than 2-3).

- Mon Nov 14, 2016 11:12 am #58139 Answering my own questions:

1. Connecting TX0 (output) to a 5V serial device -- It seems to work fine. I have connected it this way, and I have several days run time on it, including 8 hour + runs. Still fine. I am *not* suggesting or implying that it is OK to connect an *input* this way.

2. Running external devices from the 5V USB power via the Pin Connector. -- Unknown to me at the time, one of the displays I have is drawing excessive current (over 1A). When I connected it this way, the USB power diode got very hot almost immediately, but it survived. I think 500mA is probably even too much to try to pull this way. Right now, for the prototype, I have a long USB wire connected to the display, which is in turn connected to the NodeMCU development board -- in other words, using the diode as intended -- to prevent back feeding a connected USB host.

3. There are lots of ESP8266 development boards out there, some include un-soldered pins. If I build more than the 2 I have now, I will do more research before buying then next batch of ESP8266 boards.