ESP8266 Community Forum

- Mon Jan 01, 2018 6:37 pm #72819 You can use multiple SPI devices on the ssmr bus, but each device needs an enable pin. I2C is more efficient as far as pins are concerned, but have more overhead timewise.

- Tue Jan 02, 2018 7:42 pm #72843 Thank You for your respond. I have a 5.0 LCD 20x4 I am waning to add to the i2c bus. I used a logic leveler. When you do a scan for i2c ports it shows up when it is power by 3.3 volts. but when you use 5.0 on the high side is does not show up. Maybe I have the logic leveler wire wrong. I just put 5v on the high side.

Sprinkfitter

- Tue Jan 02, 2018 9:49 pm #72844 I have tried logic shifters that use a mosfet (and resistors) to do the level translation. I have had poor success with these. Now I use chips designed for that function. One chip I use a lot is NLSX4373 https://www.onsemi.com/pub/Collateral/NLSX4373-D.PDF

When I tried the mosfet shifter I was getting a distorted waveform. The front edge of the transition wasn't coming up well. It may have been a mosfet that wasn't appropriate for that use. The level shifting worked but it messed up the front edge. If I were to use a multimeter to see the levels it would show the full shift. But it wasn't good enough for the device I connected to it.

- Wed Jan 03, 2018 10:11 am #72856 I have been playing with the 20x4 lcd on the i2s bus line all night. I have look online and read about using this I2C Logic Level Converter Bi-Directional Module 5V to 3.3V TE291. I was never able to get the address of the lcd when using it. What I did do was use the esp8266 12r Vin pin and when I power it with the usb 5volts I was able to get the address of the lcd. The vin pin will only produce about 4.3 to 4.6. Clearly not enough to drive the Lcd. Any ideas what I am doing wrong. Being able to have 3.3 and 5.5 will be very helpful.