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SPI confusing SPI_Xfer().

 
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SPI confusing SPI_Xfer().
PostPosted: Thu Oct 15, 2009 3:24 am     Reply with quote
I use the hardware spi on the pic.

I have a module where one pin is to enable this module before the SPI communication start.
I expect the Enable=PIN_A3 to activate pin A3 before the SPI function invoked, but in the list file it not look like, expect SPI_Xfer().
Code:
#use spi(Master,SPI1,Force_HW,Enable=PIN_A3)

Will it say: SPI_Xfer() is using the setup from #use spi().
-And SPI_Read/SPI_Write just use the hardware reg.

The function SPI_Xfer is a much longer asm code compared to SPI_Read/SPI_Write, but the feature Enable= and other things only work on the function SPI_Xfer()?




Guest
PostPosted: Thu Oct 15, 2009 3:50 am     Reply with quote
This is from the startup code in main, think there is a bug:

Why is pin A3 = high when the SPI is not active?
Code:
#use spi(Master,SPI1,Force_HW,Enable=PIN_A3,ENABLE_ACTIVE=1)

0224: BCF TRISA.3 -> output, ok
0226: BSF LATA.3 -> why not low?

I change ENABLE_ACTIVE=0 but no change in lst. file.
PCM programmer



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PostPosted: Thu Oct 15, 2009 12:28 pm     Reply with quote
Quote:
Will it say: SPI_Xfer() is using the setup from #use spi().
-And SPI_Read/SPI_Write just use the hardware reg.

#use spi() uses spi_xfer(). setup_spi() uses spi_write() and spi_read().
Do not mix the two methods.

Quote:
The function SPI_Xfer is a much longer asm code compared to SPI_Read/SPI_Write, but the feature Enable= and other things only work on the function SPI_Xfer()?

With setup_spi(), you must handle the Chip select for the slave with
your own code. Use output_low(CS_PIN) and output_high(CS_PIN).

Quote:
I change ENABLE_ACTIVE=0 but no change in lst. file.

Post your PIC and your compiler version.
Guest
PostPosted: Fri Oct 16, 2009 1:07 am     Reply with quote
Thanks for the explanation:-)
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