These are chat archives for esp8266/Arduino

28th
Jun 2017
Bert Melis
@bertmelis
Jun 28 2017 14:36
What are the output characteristics of the device you're talking too?
As you're using 1,8/3,3k resistors, the device should deliver 1mA while high.
brutzler
@brutzler
Jun 28 2017 16:38
Think the device can deliver the 1mA, because I can measure 5V-level on the input of the voltage devider.
But I think, that the WEMOS D1 has a somehow internal resistor, that is parallel to the 3,3k and makes him to ~450R.
Then Ohms law will be correct again....
Just ordered some 3,3V Z-diodes. Try to place them instead of the 3,3k resistor and make the 1,8k bigger to ~10k.
grafik.png
Like this picture
Last solution would be a level-shifter.
Bert Melis
@bertmelis
Jun 28 2017 18:02
It does have an internal pullup, but you have to enable it, and it's of magnitude 30k-100k.
Bert Melis
@bertmelis
Jun 28 2017 18:12
OH, you're using the real rx/tx? Not softwareserial? The Wemos has a 470R on these pins.
brutzler
@brutzler
Jun 28 2017 19:18
Yes, just seen it, but the 470R is going into the CP2102. Thought this is only a problem during flashing.
But I presume its internal pulled to GND. Then it makes somehow sense, because 3,3k||470R makes ~411R. And this results only 1V @ the RX-pin.
brutzler
@brutzler
Jun 28 2017 19:26
BTW: does anyone know a good circuit simulator? online or offline
brutzler
@brutzler
Jun 28 2017 19:36
Besides LTSpice