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bwhiten
Joined: 26 Nov 2003
Posts: 151
Location: Grayson, GA
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| SPI Slave Select and Interrupt |
 Posted: Wed May 14, 2008 12:08 pm |
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I can't seem to find much information in the forum on SPI Slaves and even less in the CCS help files. In particular I would like to know if the #INT_SSP on a Slave PIC is set by the state of Slave_Select or just by activity on the SPI clock lines. I want to use Slave Select to help frame complete data transfers between PICs.
Second question, I tried to use the SPI1 parameter in the Slave #use spi() statement but it errored out with Option Invalid, Not valid for H/W.
Is this because a slave must use the H/W SPI?
Slave = 16F887
Master = 18F67J50
Version 4.073 |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed May 14, 2008 12:24 pm |
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| Quote: |
I would like to know if the #INT_SSP on a Slave PIC is set by the state of
Slave_Select or just by activity on the SPI clock lines |
Look at the following timing diagram in the PIC data sheet.
It shows that SSPIF is set soon after bit 0 is received. This means you
get an interrupt when a complete byte has been received by the slave.
| Quote: | | FIGURE 13-3: SLAVE SYNCHRONIZATION WAVEFORM |
| Quote: |
I tried to use the SPI1 parameter in the Slave #use spi() statement but it
errored out with Option Invalid, Not valid for H/W. |
See this link:
http://www.ccsinfo.com/forum/viewtopic.php?t=34214 |
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bwhiten
Joined: 26 Nov 2003
Posts: 151
Location: Grayson, GA
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| Posted: Wed May 14, 2008 12:45 pm |
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Thanks for the help....again 
I had found that link and tried adding the MSB_FIRST parameter but it still won't let me add SPI1:
| Code: | | #use spi(SLAVE, MODE = 0, BITS=8, MSB_FIRST, SPI1) |
According to the help file if you use the SPIx parameter that automatically assigns the HW pins as the SPI interface. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed May 14, 2008 1:14 pm |
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I don't know. There has got to be some combination of parameters
that will make it work. Or maybe it's a bug. I've tried for a while and
I don't have any more time to spend on it. |
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bwhiten
Joined: 26 Nov 2003
Posts: 151
Location: Grayson, GA
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| Posted: Wed May 14, 2008 1:18 pm |
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Thanks very much for the help.
Maybe someone else has seen this. I will submit a question to CCS but I've not had a lot of luck getting responses lately. Plus email notices from posts I'm part of no longer works :( |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Wed May 14, 2008 3:51 pm |
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| I can not find a reference to the SPI1 parameter in the manual. Where did you read about it? |
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Ttelmah
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| Posted: Thu May 15, 2008 2:32 am |
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Look under #USE SPI in the manual.
The 'older' setup_SPI command works fine. I'd suggest just using this, since the only real advantage of the #use form, is when dealing with multiple SPI ports, or wanting to perform software SPI.
Best Wishes |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Thu May 15, 2008 5:54 am |
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| Ttelmah wrote: | | Look under #USE SPI in the manual. |
Yes, that's what I figured but I can't find this parameter. A search of the document didn't find it either.
I have the Version 4, August 2007 manual.
I also checked the latest versions of the PCWH and PCWHD manuals on the CCS website and can't find the parameter.
Strange. For the PICs with more than one SPI unit I would expect there to be a parameter to indicate which hardware unit to use. |
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Ttelmah
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| Posted: Thu May 15, 2008 7:42 am |
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A quick check through some versions:
4.027 - Doesn't even have a #use SPI entry
4.042 - Has the entry, but without SPI1/SPI2
4.051 - Has it mentioned in the 'readme', but not in the manual
4.059 - Has SPI1/SPI2 in the manual.
Critical date, seems to be about October 2007.
Best Wishes |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Thu May 15, 2008 8:47 am |
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| Can you tell me where you downloaded these manual versions from? The only manual I can find on the CCS download page is the 4-Aug-2007 version. |
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Ttelmah
Guest
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| Posted: Thu May 15, 2008 9:58 am |
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Just the versions that come with the actual compiler downloads. The separate versions available for download, seem to be months out of date...
Best Wishes |
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bwhiten
Joined: 26 Nov 2003
Posts: 151
Location: Grayson, GA
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| No email again |
| Posted: Thu May 15, 2008 11:48 am |
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Again, I received no email notice of these responses. I see the SPI1, SPI2 parameter in the help file of the compiler under the #use spi heading.
I was trying to use the #use spi command that allowed me to use the spi_xfer() command instead of spi_read and spi_write.
What method of assigning pins to the correct H/W spi is used if I only declare with the setup_spi() command? |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu May 15, 2008 12:09 pm |
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The setup_spi() function automatically uses the hardware SPI pins.
It will only work the those pins. It only does hardware SPI. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Thu May 15, 2008 12:35 pm |
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Ttelmah, thanks for the info. I didn't know in the automatic downloads more up to date versions of the manuals are included.
Bwhiten, thanks for the CCS help function tip. I forgot about that one.
| Quote: | | What method of assigning pins to the correct H/W spi is used if I only declare with the setup_spi() command? |
setup_spi() uses the first HW unit (on pins C3, C4 and C5)
setup_spi2() uses the second hardware unit if present.
For defining the SPI mode I always use the defines below instead of the CCS definitions: | Code: | #define SPI_MODE_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_H_TO_L | SPI_XMIT_L_TO_H) |
So setting up your slave becomes: | Code: | | setup_spi(SPI_SLAVE | SPI_MODE_0 ); |
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bwhiten
Joined: 26 Nov 2003
Posts: 151
Location: Grayson, GA
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| How about the master setup? |
| Posted: Thu May 15, 2008 8:39 pm |
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| ckielstra wrote: | For defining the SPI mode I always use the defines below instead of the CCS definitions: | Code: | #define SPI_MODE_0 (SPI_L_TO_H | SPI_XMIT_L_TO_H)
#define SPI_MODE_1 (SPI_L_TO_H)
#define SPI_MODE_2 (SPI_H_TO_L)
#define SPI_MODE_3 (SPI_H_TO_L | SPI_XMIT_L_TO_H) |
So setting up your slave becomes: | Code: | | setup_spi(SPI_SLAVE | SPI_MODE_0 ); |
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What is the SPI_XMIT_L_TO_H used for and how would you set up a master using these #defines ?
Thanks again. |
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