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geokonst
Joined: 04 Apr 2009
Posts: 27
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 Posted: Fri Apr 17, 2009 7:10 pm |
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OK I really have no words to thank you enough FvM.
I've been pulling my hair trying to make this work for a month now. You did it man!
Oh the joy!!!!
Thank you so much!!!!!!
THANK YOU! |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Sat Apr 18, 2009 3:35 am |
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I'm glad, that the problem could be solved finally.
Now I have supplement regarding changes in V4.091.
I previously suggested to use spi_read only because of a bug in status bit handling with spi_write().
| Code: | SPI_nCS_LAT = 0;
spi_read(0xAB);
spi_read(0);
spi_read(0);
spi_read(0);
bID=spi_read(0);
SPI_nCS_LAT = 1; |
In V4.091, SPIxTBF is handled correctly, but my original code is still not working due to another non-obvious issue.
| Code: | spi_write(0xAB);
spi_write(0);
spi_write0);
spi_write(0);
bID=spi_read(0); |
The code is intended to write 4 bytes (a command and 3 dummy bytes) and then read one byte in the fifth cycle.
| Code: | .................... spi_write(0);
05D1C: CLR.B 248
05D1E: BTSC.B 240.1
05D20: BRA 5D1E
05D22: BCLR.B 240.6
.................... bID=spi_read(0);
05D24: CLR.B 248
05D26: BTSS.B 240.0
05D28: BRA 5D26
05D2A: MOV.B 248,W0L
05D2C: BCLR.B 240.6
05D2E: MOV.B W0L,17F1 |
In the above assembly listing of part of the code, bID doesn't return the result of the last SPI cycle as expected.
This happens because spi_write() resets SPIROV (240.6) before the first byte is received, spi_read(0) doesn't wait for the second cycle to finish but returns the read data from previous cycle immediately. The problem can be handled by inserting a dummy spi_read() before the spi_read(0), or by using spi_read(xx) only, as I did before.
I won't say that it's actually a bug, but a problem involved with the status bit handling in PCD built-in SPI functions. But it must be expected to confuse PCD users seriously. |
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FvM
Joined: 27 Aug 2008
Posts: 2337
Location: Germany
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| Posted: Mon Sep 14, 2009 2:34 pm |
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As a late update, I realized that PCD is using the mask value SPI_H_TO_L in a different meaning than the 8-Bit compilers. Thus my above coding of SPI modes isn't correct. What I declared as SPI MODE_3 is actually setting mode 0. It's no problem with SPI flash, that supports both modes. This is a corrected mapping of SPI modes.
| Code: | #define SPI_MODE_0_0 0x0100
#define SPI_MODE_0_1 0x0000
#define SPI_MODE_1_0 0x0140
#define SPI_MODE_1_1 0x0040 |
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