read16 has bytes swapped?

[xlfe]

I used your code to read from a bmp280, but I kept getting strange values - I traced it back to the read16 function - it looks like the bytes were being read in reverse order?

xlfe@98e453d#diff-1123c8cab49efa03f9998c97c9d6c2d0

[tomtor]

It was quite some time ago I wrote that code. I cannot remember exactly how I tested it, so thanks for your feedback. I will probably have a look at it, at a later time, because I am currently busy with other projects.

[xlfe]

@tomtor of course - just happy having logged an issue to help anyone having similar problems. Thanks for your initial code - it helped a lot getting the esp32 to do what I wanted!

[DominicD]

@xlfe I want to read data from a bme280. Is your code open source? Or any chance I could get the relevant parts?

Edit: Just found your repository. Thanks for both of your work!

[xlfe]

Hi yes it's here https://github.com/xlfe/ulp-i2c

…

On Fri, 22 Jan 2021, 10:20 pm DominicD, ***@***.***> wrote: @xlfe <https://github.com/xlfe> I want to read data from a bme280. Is your code open source? Or any chance I could get the relevant parts? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#3 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAI7RO7CZDEUWPEWFNYHYATS3FNOJANCNFSM4FMUBBFA> .

[HareshPrajapati]

is that any working example for bme280 using spi-ulp

[HareshPrajapati]

Hi yes it's here https://github.com/xlfe/ulp-i2c
…
On Fri, 22 Jan 2021, 10:20 pm DominicD, @.***> wrote: @xlfe https://github.com/xlfe I want to read data from a bme280. Is your code open source? Or any chance I could get the relevant parts? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#3 (comment)>, or unsubscribe https://github.com/notifications/unsubscribe-auth/AAI7RO7CZDEUWPEWFNYHYATS3FNOJANCNFSM4FMUBBFA .
is that any working example for bme280 using spi-ulp

[tomtor]

I used your code to read from a bmp280, but I kept getting strange values - I traced it back to the read16 function - it looks like the bytes were being read in reverse order?

Hi @xlfe

It has taken a long time, but I dusted off this project and running the current code for BMP180 and it prints the correct pressure and temperature.

When I compare

https://github.com/adafruit/Adafruit-BMP085-Library/blob/cd9a26bc77c1fdbd261fb392a50065d249a4fb98/Adafruit_BMP085.cpp#L128-L132

and

ulp-i2c/main/ulp_example_main.c

Line 98 in 6c7996d

int32_t UP= ((((ulp_pressure & 0xFFFF) << 8) | (ulp_pressure2 & 0xFFFF)) >> (8-oversampling));

the code looks identical, so my read16() is producing a similar result as the Arduino read16.

Correct byte order is always a tricky issue, but compatibility with existing Arduino code is nice, so I don't think the bytes are reversed. You are also the only one reporting this issue.

If you don't agree or have other suggestions, please let me know, because I might be missing something.

[tomtor]

No recent activity, code verified to run correctly.

[tomtor]

Did some more research, I2C 16 bit transfers are most significant byte first, which is implemented in read16 and write16.