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beaker404
Joined: 24 Jul 2012
Posts: 163
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| Two SPI streams, same mode |
 Posted: Fri Jul 08, 2022 12:55 pm |
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PIC18F26K22
CCS version 5.094
Tilt sensor SCL3300
EEPROM 93LC66 in 8bit mode
I have the above two devices on SPI2 of a 18F26K22.
my SPI set up is as follows:
| Code: | #use spi(master, SPI2, mode=0, baud=2000000, stream=SPI2_TILT, bits=32, MSB_FIRST) // SPI Call for Tilt Sensor
#use spi(master, SPI2, mode=0, baud=2000000, stream=SPI2_EEPROM, bits=8, FORCE_SW) // SPI Call for EEPROM |
both devices are mode 0 just different speeds and different select lines.
The select line for the Tilt sensor is C1 and the select for the EEPROM is A2.
separately, each chip works fine. The tilt sensor will work fine with the EEPROM hardware present and the EEPROM stream defined.
Problem is the EEPROM will not work properly with the Tilt stream defined, comment it out and the EEPROM works fine even with the Tilt chip connected to the SPI. Problem is, I am only reading 0xFF from the EEPROM with the Tilt stream defined.
There seems to be a lot of discussion about two streams using use_spi calls. Is this still a problem on the 5.094V and the PIC18F26K22?
Is the work around to use the SETUP_SPI method?
I can post more code if needed, just starting with the use_spi questionable behavior with two streams.
I do not think there is a way to just use one stream for the two devices as the tilt sensor wants 32b data and is quite particular about data transfer timing. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19513
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| Posted: Fri Jul 08, 2022 1:05 pm |
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Specifying SPI2, says 'FORCE_HW'. Get rid of this for the second channel,
and specify the pins.
An SPIx selection specifies to use the physical hardware, |
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beaker404
Joined: 24 Jul 2012
Posts: 163
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| Posted: Fri Jul 08, 2022 1:22 pm |
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Probably doing this wrong, but here is how I interpreted your comment:
| Code: | #use spi(master, SPI2, mode=0, baud=2000000, stream=SPI2_TILT, bits=32, MSB_FIRST) // SPI Call for Tilt Sensor
#use spi(master, DO=Pin_B3, CLK=PIN_B1, DI=PIN_B2, mode=0, baud=2000000, stream=SPI2_EEPROM, bits=8, FORCE_SW) // SPI Call for EEPROM |
Still reading 0XFF from the EEPROM. The EEPROM setup does work with the TILT setup disabled as before. |
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beaker404
Joined: 24 Jul 2012
Posts: 163
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| Posted: Fri Jul 08, 2022 2:27 pm |
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OK
Here is what worked and everyone (Tilt Sensor and EEPROM) are being nice neighbors and working correctly now.
| Code: | #use spi(master, DO=Pin_B3, CLK=PIN_B1, DI=PIN_B2 ,mode=0, baud=2000000, stream=SPI2_TILT, bits=32, MSB_FIRST, FORCE_SW) // SPI Call for Tilt Sensor
#use spi(master, DO=Pin_B3, CLK=PIN_B1, DI=PIN_B2 ,ENABLE_ACTIVE=1, ENABLE_DELAY=20,mode=0, baud=100000, stream=SPI2_EEPROM, bits=8, FORCE_SW) // SPI Call for EEPROM |
The thing that made it all start working was taking the SPI2 setup out of the TILT stream setup. I also added a line to my main that allowed PIN_A2 to float.
Still open for discussion on why this works. Otherwise I will take it as a coding mystery that just is. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Jul 08, 2022 2:45 pm |
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CS on the tilt sensor is low true. CS on the eeprom is high true.
Does your code do this ? You never showed us your code for that.
Also, you did more than just remove 'SPI2' from the tilt sensor stream.
You made it into software SPI so both streams are now software SPI.
I'm wondering if the CS active levels are the cause of the whole problem. |
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beaker404
Joined: 24 Jul 2012
Posts: 163
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| Posted: Fri Jul 08, 2022 3:24 pm |
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True, I did only change one thing at a time, just posting where I was at when it all started working, I will start taking other stuff out.
I bit bang the CS pins. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Fri Jul 08, 2022 3:31 pm |
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I understand that you bitbang CS. But do you set CS active high for the eeprom ? ie:
| Code: |
output_high(EEPROM_CS);
spi_xfer(etc);
output_low(EEPROM_CS)
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Ttelmah
Joined: 11 Mar 2010
Posts: 19513
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| Posted: Mon Jul 11, 2022 2:03 am |
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There is a key bit of understanding here.
If a _peripheral_ has control of a set of pins, the output ones cannot
be used for normal I/O.
So a software SPI cannot be run on the same pins as a hardware SPI,
while the latter is enabled.
This setup:
| Code: |
#use spi(master, SPI2, mode=0, baud=2000000, stream=SPI2_TILT, bits=32, MSB_FIRST) // SPI Call for Tilt Sensor
#use spi(master, DO=Pin_B3, CLK=PIN_B1, DI=PIN_B2, mode=0, baud=2000000, stream=SPI2_EEPROM, bits=8, FORCE_SW) // SPI Call for EEPROM
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Will merrily work, _but_ you have to disable the hardware stream
before you use the software stream. Use the spi_init command to disable
the hardware module before you talk to the software SPI.
| Code: |
spi_init(SPI2_TILT, FALSE);
//now you can use the EEPROM stream.
//Then when you have finished with the EEPROM use
spi_init(SPI2_TILT, TRUE);
// to re-enable the hardware SPI
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It does all seem silly though. Why not just use the same stream for both
devices?. Set up just the single stream with 32bit selected, and use this
for both devices. Just specify to only transfer 8 bits in the spi_xfer
commands for the EEPROM device. Optional last value for this is the
number of bits to actually send. |
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