Multiple BME280 on same SPI bus

snisse

Hello

Im planning on addind som temperature and humidity sensors for monitoring build chamber and spool chambers. I saw in the documentation that BME280 should be supported, but im wondering if its possible to add them on the same SPI bus or if i should wire them separately?

This is the sensor im planning on using

https://www.amazon.se/barometriska-temperatur-luftfuktighet-temperaturfuktighetssensor-fukttemperatursensormodul/dp/B0C4L8BKJP/ref=asc_df_B0C4L8BKJP/?tag=shpngadsglede-21&linkCode=df0&hvadid=476443254436&hvpos=&hvnetw=g&hvrand=6489179680714811170&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1012511&hvtargid=pla-2200276659493&psc=1&mcid=8c4311efe9033d3494654b062d364c9f

I havent found any info if its possible to wire them on the same bus, and if its not, is there any limit on how many i can connect seperately?

dc42

@snisse we've not tested multiple BME280 sensors but they should work with the following caveats:

BME280 is supported on Duet 3 series main boards only, not on Duet 2 or Duet Maestro. They may also work on Duet 3 expansion boards that support an SPI bus such as the EXP3HC.
Each BME280 must use a different CS signal. There are 4 CS signals on the daughter board connector on the 6HC and 6XD, and 2 on the Duet 3 Mini.
There is a limit to the maximum length that the SPI bus may have before the signals are degraded too much.

snisse

@dc42 Ok great, thanks for the reply. Then i guess i can report back ones i have tested.

I have a 6HC and a EXP3HC, but if i under stand you i should be able to share the MISO, SCK, and MOSI pins to different sensors, and then have CS0 to one and CS1 to another etc? How is it with the 3.3 supply, how much current can that handle?

Do you know the maximum lenght? Im planning on running shielded wires so hopefully it should be fine.

dc42

@snisse yes you can use CS0 and CS1, and the 3.3V rail can easily power two sensors. The total cable length should preferably be no more than 200mm, but 400mm will probably work.