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norbert-walter / esp32-nmea2000-obp60

nmea2000 gateway with ESP32
GNU General Public License v2.0
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Jumping values for BME280 values #44

Open norbert-walter opened 2 years ago

norbert-walter commented 2 years ago

Jumping values for BME280 values from time to time. The problem is not located. Fake chips from China?

norbert-walter commented 2 years ago

New information about the problem. The signals on I2C bus are not correct in the voltage level. Any low level bits have a very short spike to high level. The problem coming after a warm up phase of the electronic but not always. After power down and a waiting time is the function correct. I mean it is a problem with the I2C function in the ESP32. I want to check the pull up resistors on SCL and SDL lines.

grafik

grafik

norbert-walter commented 2 years ago

I think I know what the problem with the BME280 is related to the I2C bus. The module can be supplied with both 5.0V and 3.3V. For this to work, there is a voltage converter XC6206P332MR-G (U4) from 5.0V to 3.3V on the board. If you now use a supply voltage of 3.3V, which is possible according to the description, then it must also go through the voltage converter. The input voltage is reduced again by approx. 0.25...0.68V. In the worst case, only 2.62V arrive at the BME280. Under certain circumstances, this may not be enough for the chip to still function correctly on the I2C bus. It is noticeable that everything works as desired in the cold state shortly after switching on and that problems occur with increasing heating or over a period of time. To avoid this, the BME280 module would have to be supplied with 5.0V. I will do the construction again on a breadboard and operate the BME280 module with 3.3V and 5.0V and check how it behaves there.

grafik Schematic BME280 Modul