Sunday 26 August 2018

#BAW!! Weeks 5 Lets try a new IC (Part 1 finding the data)

Still running quite far behind the Bubble watch from week 4 is still an in progress project I'll keep everyone updated as I get more work done on it.

Sometimes a change is as good as a rest so its now time to try a new approach. What about a new IC at this point i'm going to pick something new from Mousers website ( mouser is a component disributer I like their new product search )

First item i have found on the page is a new accelerometer from Bosch Sensortech according to the page it was shown of at the most recent CES and receiving awards for innovation. This is many due to its ultra low operating of around 8uA (super low) thats about 20 time lower than their other Accelerometers at around 150uA operating current.

Its always funny with brand new IC products the offer very little information to even Bosch-Sensortec's own page has very limited technical detail. 

These are the only two documents available at this moment in time:  

A nice give away is the schematic on the shuttle board document which shows how the device is decoupled, and give an idea of how its supposed to be connected as typical application.

Another thing to do is look at the previous generation of the device. At the moment Bosch manufacture the BMA280 which is the previous accelerometer device from them.

I took a look at the datasheets of other Bosch devices and discovered the register map for the device are for the most part identical. This will be a good reference from bringing up this device. 

Time to start making a symbol for the part. I have the Pinout.

I draw it into the KiCAD symbol editor I also find it useful to make sure the do not connect pins are drawn in they can be useful for reference later and making sure the footprint is correct. KiCAD can suggest the correct footprint based on the number of pins so it useful to have everything in front of you.

Time to work on a footprint for the part. I am using the datasheet for the BMA456 being one of the more recent accelerometers i can use the application notes to help draw in what I need for this board.    

schematic is now done leaving enough landings for pull up resistors and jumper links to select the different communication modes. The BMA400 supports both I2C and SPI protocols and there is also an I2C address select. 


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