2009-01-18 06:37:37     SPI testing

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2009-01-18 06:37:37     SPI testing

ivan ucles (GERMANY)

Message: 68066   




I try to send SPI messages between a CM-BF537 board and a STAMP 537 board without succes so far.


In both boards i´ve added the bfin5xx driver and the spidev driver. And i have initialize a device on bus "0"


and CS "1" spidev0.1.


I connect MOSIs, MISOs and  CLKs of both boards.


The CM-BF537 is supposed to be the master, so i connect de SSEL chip to 5v. and its CS1 to the SSEL chip


of the STAMP.


When i try to send a message using the example included in spidev kernel documentation, i get


response(2, 3): ff ff




What am i missing? could somebody help me?


Thank u




2009-01-18 10:12:07     Re: SPI testing


Message: 68068   




Just to make sure -- SPI is a master/slave type set up. only one controlls the clock (connect CLKS together) - Master Out (MOSI) needs to be connected to Slave In (MOSI), and Master In (MISO) needs to be connected to Slave Out (MISO).


Plus - the Blackfin is a 3.3V device ONLY - 5V may damage the part.






2009-01-18 12:52:20     Re: SPI testing

Mike Frysinger (UNITED STATES)

Message: 68070   


also, the linux kernel does not support slave mode operation.  so if you want to have one be a slave, you'll have to write your own driver or extend the existing framework.





2009-01-18 15:09:39     Re: SPI testing

ivan ucles (GERMANY)

Message: 68072   




thanks for the answer.


Where could i find some information about how to write the slave-part driver?


Could i take another similar driver as template? which one?


About the voltage, i connected SSEL to another pin29 of x8 connector.


Should i connect it then to pin number 9 which is 3.3v right?


Thank you!




2009-01-18 15:39:31     Re: SPI testing

Mike Frysinger (UNITED STATES)

Message: 68074   


unfortunately, there isnt much info as i dont think anyone has thought too hard on the idea.  might be easier to start out with a simple char driver and program the SPI controller yourself.




2009-01-19 03:17:28     Re: SPI testing

ivan ucles (GERMANY)

Message: 68085   


And if i configure both boards as master (with both SSEL to  3.3v and no CS)


can they interchange messages? throug which device?




2009-01-19 03:20:58     Re: SPI testing

Mike Frysinger (UNITED STATES)

Message: 68086   


like Robin said, only one device can be the master at any one time.  that is simply how SPI works.