ESP8266 Community Forum

- Sun Jan 31, 2016 5:56 pm #40123 I am having trouble getting and level shifting to work between a Renesas SH7055 micro and the ESP8266.
I have two different types of level shifter from EBay.
If I connect the TX/RX on the SH7055 to a 5V FT232R USB-Serial I can send and receive data without a problem.
If I connect the FT232R to the level shifter I can send and receive between the PC and ESP8266 without a problem.
If I connect the SH7055 to the level shifter I can send commands to the SH7055 without a problem but the response is not correct, sometimes I get the correct data back, other times I get part of the data or garbage.
I have tried adding a 10K pull-up to 5V on the TX from the SH7055, this has not helped.
If I connect the TX and RX on the 5V side of the level shifter I get everything echoed back to the ESP8266 without a single bit out of place.

It is almost like the TX signal is weak
Any ideas ?

- Mon Feb 01, 2016 8:51 pm #40217 Yesterday I tried several other methods for the level shift between 5v and 3.3v
I used a voltage divider with a 200 ohm and 100 ohm resistor, this didn't work.
I wired up a 74HC245 to convert the 5v to 3.3v for the RX, this also gets garbage back to the ESP8266.
When I connect a FT232R to the 74HC245 I can program the ESP8266 without a problem so the 74HC245 is working.

I even wired up a MAX3390 level shift chip, this fails between the SH7055 and ESP8266 but works between the 5v FT232R and the ESP8266.

As a last test I connected the TX and RX from the ESP8266 to RX1 and TX1 on a leaf maple mini and connected RX3 and TX3 on the maple mini to the TX and RX of the SH7055. I loaded a simple program into the maple mini that send everything from RX1 to TX3 and everything from RX3 to TX1.
The maple mini is 5V tolerant on the RX3 and TX3 so no level shifting is required.
This works perfectly, I get exactly what I should on the ESP8266.

I have tried a different ESP8266 board and a different SH7055 board, same results.

The SH7055 is in an engine management system, it has a sensor ground and battery ground, these are both connected together on the test bench and this ground is connected to the ESP8266 and level shifter ground.

- Tue Feb 02, 2016 10:09 am #40269 You can try basic level shifter like this one :

- Tue Feb 02, 2016 1:52 pm #40289 I already tried the 2N7000 and this didn't work.
I have ordered some TXS0102 IC's to try next.