Matrix user forums

Morning

I am working on a project that has a 3.3 Volt IC - MPU9250 9-axis (9DOF) accelerator, gyroscope, and digital compass (magnetometer)
My Breakout Board spec is:

VCC......3.6 to 6V supply (on-board 3.3V regulator)
GND......0V
SCL......I2C serial clock
SDA......I2C serial data
EDA......Auxiliary I2C master serial data
ECL......Auxiliary I2C Master serial clock
AD0......I2C Slave Address LSB (AD0)
INT......Interrupt digital output (totem pole or open-drain)
NCS.....Chip select (SPI mode only)
FSYNC..Frame synchronization digital input. Connect to GND if unused.

I have a few uncertainties as not done a great deal with I2C or SPI I know level shifters exist, do i need them ? could i get away by putting the pull up resistors on the 3.3 Volt side ? as 3.3 Volts will still be detected as a "High" or this this a bit iffy ?

i am also wanting to use the INT to monitor when the IC Detects movement , and unsure I2C or SPI , but if i go SPI i have the chip select voltage isse again

Or should i just use a shifter ?

https://uk.rs-online.com/web/p/voltage- ... s/7092545/

Steve

Hi Steve,

Depends on the chip limits - but I would use a level-shift. They are easy to use, and in my experience, work very well. There are various options depending on the number of signals needing shifted (and also speed).
You could also use a voltage divider - using a couple of resistors - but this is just one-way (so i2c 5v mcu to 3.3v) 3.3v would probably be recognised as high by most MCUs?
If the chip limits allow it - things may work well without. But 5v into 3.3v may release the magic white smoke that makes all electronics work?

Martin

Why not use a controller that runs on 3v3 and forgo any level shifting?

Hi Martin

mnf wrote:
the magic white smoke

- thats what i am trying to avoid, been there done that
Have been looking at it this afternoon, decided for a couple of Quid might as well better safe than sorry - trying to do it on the cheep dosnt always work

kersing wrote:
Why not use a controller that runs on 3v3 and forgo any level shifting?
Got other things that are 5 Volts connected to my micro

any recommendation of a level shifter (DIP preferred) , considering the one above from RS

Steve

Try the TXS0108E - doesn't seem to be available in PDIP package - but there are breakouts available (https://www.amazon.co.uk/AZDelivery-Bi- ... 5v+to+3.3v) for experimentation.

For i2c (or UART to bluetooth for example) the very cheap 4 channel bi-directional boards work well - they might not be quick enough for SPI.. (for example https://www.amazon.co.uk/ARCELI-Channel ... al-Shifter )

Less ICs available in DIP package - see: https://uk.farnell.com/w/c/semiconducto ... -style=dip

Martin

Thank You i will go have a look at those
'
Steve

:Edit

Just had a nosey on a site i use for various bit and bats must admit i didnt check here first
(Not as cheep as Amazon, but at least you have access to support, drawings, schematics etc.)

https://www.artekit.eu/products/breakou ... -breakout/

this was also linked

https://www.artekit.eu/using-logic-level-converters/

i hadn't seen the artekit site before - I usually use CPC (sometimes microchip - but postage is a bit severe for small orders) - but looks very useful. Links to docs etc make life much easier!

Martin