only necessary for i2c, not serial or even spi

just connect them together with two resistors like this page says: http://michaelteeuw.nl/post/113107637802/esp8266-no-strings-attached ESP8266’s VCC is connected to a 3v3 power supply. ESP8266’s GND is connected to the ground. ESP8266’s RXD is connected to Arduino’s pin 4 using a voltage divider (330Ω to GND, 170Ω to pin 4). ESP8266’s TXD is connected to Arduino’s pin 5 (The Arduino can handle 3v3 just fine.) ESP8266’s CH_PD is connected to VCC using a 10k pull up resistor. (This will enable the wifi module.) On Fri, 5 Feb 2016, robb wrote: i've discovered 5v (arduino) to 3.3v (esp8266) serial requires a logic > level shifter. > i have a max3243 with no idea how to use it. > > anyone know how to use a Multichannel RS-232 Line Driver/Receiver or > know a good circuit schematic that converts 5v-3.3v logic? > > thx > ~r > >

@jake guess it's time to dig through the resistor box...i'm worried about you can use a single resistor instead (from 5V TX to 3.3V RX) but it should be bigger, like 10K if that works, but not less than 1K. hmm, chip-power-down (CH_PD) wants 10kΩ > vcc...i didn't know that. if you see other diagrams where CH_PD connects directly to Vcc it is probably fine. also 10K is just a random number, anything from 1K to 100K would probably have the same effect. -jake