BME280 burst data readout

[phoreglad]

Hi,

I want to use IN100 to read data from BME280 sensor, but my current application expects to receive the data from all 8 registers instead of 6 as it is in the example. I tried to use burst read as recommended by the datasheet in section 4 but was unable to get it to work.

My current I2C configuration is:

"i2c": {
        "sw0PwrCtl": 1,
        "coldBootEn": 1,
        "warmBootEn": 1,
        "sclPin": 4,
        "sdaPin": 5,
        "addrBit": 7,
        "speed": 400,
        "slvAddr": 119,
        "memStoreLen": 8,
        "memStoreOffset": 0,
        "cmd": [
            "i2c wait: 3 1 27",
            "i2c tx: 3 f2",
            "i2c tx: 3 1",
            "i2c tx: 3 f5",
            "i2c tx: 3 0",
            "i2c tx: 3 f4",
            "i2c tx: 3 25",
            "i2c null:",
            "i2c wait: 3 1 4e",
            "i2c tx: 3 f7",
            "i2c null:",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c rx: 3",
            "i2c null:"
        ]
    },

Using the same command sequence on Raspberry Pi Pico works fine.

Would it be possible to add an example configuration for burst reading BME280 data registers?

[NanoBeacon]

Hi There,

Can you share more details about it not working? Are you seeing no data being read back at all? There is a known issue with multiple read commands being sent a row where at most 5 read commands will work before a new write command must be issued.

[phoreglad]

Yes, that was what was happening. IIRC when I looked at the signals on an oscilloscope, after the last write command (0xf7) there was no activity on SCL or SDA lines. Later today I can add a picture from the scope to show exactly what's going on.

[phoreglad]

As promised I'm attaching pictures from my scope. Channel 1 - SCL Channel 2 - SDA Channel 3 - SW0

First, the whole communication sequence during the SW0 active period:

Zooming to the last command shows that after it's sent the SCL and SDA lines are idle and IN100 doesn't attempt to read the data at all:

I have also checked if the register configuration commands and data read commands are sent correctly. I can attach those pictures as well if needed.

[phoreglad]

If I understand correctly splitting the read into multiple shorter ones (e.g. 3 + 5 bytes) should fix this problem, am I right?