SPI - The basics

[HenrikOlsson]

Hi,
I just took a quick look at this but as far as I can see the commands are 8 bits and the response from the device is 11 bits starting at the 9th clock pulse. So, if reading the acceleration you first SHIFTOUT the 8 bit RDAX command, then you SHIFTIN 11 bits for a total of 19bits.

[boroko]

After banging around for a while, I was able to get this to give me good data from the inclinometer:

CS_I      VAR           PORTD.0  ' chip select Inclinomteter
CS_D      VAR           PORTC.3  ' chip select D/A
SCK       VAR           PORTD.3 ' clock
SDI       VAR           PORTD.2 ' data IN , MISO
SDO       VAR           PORTD.1 ' data OUT, MOSI
IncIn     var           word
HIGH CS_I   
HIGH CS_D
LOW SCK
HIGH CS_I
'I = %00001000      'send TeMP command
I = %00010000     'send RDAX 

Main:
     GOSUB iNCrDG
     hserout ["IncRdg ",bin IncIn," ",DEC IncIn," ",10,13]
     PAUSE 100
goto main
'**** Subs *********************************
;---- Sub to read the inclinometer ------------------
IncRdg:
  LOW CS_I                       ' enable writes to Inclinometer
  SHIFTOUT SDO,SCK,1,[I]      'sends command to READ
  SHIFTIN SDI,SCK,0,[IncIn\11]  
  HIGH CS_I 
  RETURN

My LOGIC pod had a bit of a rough time trying to make sense of the unusual length of data and that threw me for a bit, but the HSEROUT showed that all was good. .

Hope that help someone.

Bo