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Question asked by nsh.sadra on Apr 11, 2017
Latest reply on Apr 12, 2017 by Miroslav B


I have designed a circuit which has 8 LIS3mdl sensor slot on 1 spi bus.
The problem when I connect only one ls3mdl sensor (other 7 are empty) to the board it works well. but most of the when I connect another one ( sometimes 2 and sometimes 3 or 4 and more) all sensor stop working. ( it reads the register values but the wrong parameter get back) in this mode, I am reading sensors one by one.(make one of SS(chip select) 0 talk to sensor and make it 1 and then do the same with next sensor). Immediately when I reduce the number of sensors to 1 it works correctly and when and more sensor it goes wrong.
I myself think that the problem appears because when SS pin for other sensors is high and it means they are in i2c mode and they talk in I2C on the bus and it makes conflicting(i saw wrong data coming in debug mode and in oscilloscope)
I once though the problem is because of low current on spi bus so I enabled only internal pull-up of Microcontroller(stm32f407vgt6) miso mosi sck and ss pins.
my SPI bus is something like the image this image. 
Can anyone help me?