MMA7455 and BS2sx

mathieugr

Hi guys,

I am trying to use a MMA7455 3 axis accelerometer module with a BS2sx. I tried the demo code for the BS2 and modified this code and both work for the BS2 (demo MMA7455L 3-Axis Accelerometer Demo (PBasic) v1.0 DEMO#2.bs2 and my code testlessvar.bs2 ). Unfortunately when I switch the chip to a BS2sx the accelerometer values always indicate -1 on all axes. I need to use the BS2sx for memory space. After looking into it, I tought it might be caused by the different transmission rates of the SHIFTIN and SHIFTOUT commands on the BS2sx (42 kbits/s instead of 16kbits/s for the BS2). Is this the problem and is there anyway I can fix it?

Thank you for your help!

Mike Green

I don't see any obvious reason why either program would give you trouble on the BS2sx when they work with the BS2. Yes, the SHIFTIN and SHIFTOUT statements clock faster on the BS2sx and the BS2sx executes code faster in general, but the MMA7455 should be capable of much higher speeds. I suspect that there's a wiring problem, particularly since the values are all one bits all the time.