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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| I can't enable Slave Select pin on 16F1508[SOLVED] |
 Posted: Sat May 09, 2015 1:03 pm |
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Hello everyone.
I am trying to run SPI interface on 16F1508 but I have problem with the hardware SS(Slave Select) pin of the SPI. Scoped the signals on SCLK SDO are fine but SS (PIN_C6) isn't moving at all. I tried many different configurations but no success at the end. Here is the code:
| Code: |
#include <16F1508.h>
#FUSES INTRC_IO, NOWDT, PUT, NOMCLR, NOPROTECT, NOBROWNOUT, NOCLKOUT, NOIESO, NOFCMEN, NOWRT, NOLPBOR, NODEBUG, NOLVP
#USE delay(internal = 16M)
#use spi(FORCE_HW, BITS=8, ENABLE=PIN_C6, ENABLE_ACTIVE=0)
#include "NRF24L01.c"
void main()
{
setup_oscillator(OSC_16MHZ);
setup_spi(SPI_MASTER | SPI_SCK_IDLE_LOW | SPI_XMIT_L_TO_H | SPI_SS_C6);
while(TRUE)
{
spi_write(0xAA);
delay_us(100);
}
}
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Any help would be much appreciated!
_________________
A person who never made a mistake never tried anything new.
Last edited by rikotech8 on Mon May 11, 2015 6:23 am; edited 1 time in total |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sat May 09, 2015 2:16 pm |
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It's an input pin on a hardware SPI slave. The hardware master doesn't
use it. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19537
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| Posted: Sat May 09, 2015 2:16 pm |
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You need to use spi_xfer, not spi_write.
There are two _separate_ ways of driving the SPI with CCS. Spi_read and spi_write are for use with the old setup_spi method, and only gives simple operation (no slave select). For #use spi, you must use spi_xfer, which can then control the select line.
If you look at the manual, you will find that setup_spi refers you to spi_read and spi_write, while #use spi refers you to spi_xfer.
You must not mix the two methods.
#use spi, can control the pin as an output for the master device.
Get rid of the setup_spi line, and use spi_xfer to send, and the code can then control this line.
On the master device, the output, can be any pin (doesn't have to be the slave select pin). |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sun May 10, 2015 2:58 am |
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Thank you guys for replies.
| Quote: | | Get rid of the setup_spi line |
Yes it works that way, but the BAUD rate is quite slower when I am not using this line, and I can't figure out why.
With this configuration:
| Code: |
#include <16F1508.h>
#FUSES INTRC_IO, NOWDT, PUT, NOMCLR, NOPROTECT, NOBROWNOUT, NOCLKOUT, NOIESO, NOFCMEN, NOWRT, NOLPBOR, NODEBUG, NOLVP
#USE delay(internal = 16M)
#use spi(FORCE_HW, BITS=8, ENABLE=PIN_C6, ENABLE_ACTIVE=0)
#include "NRF24L01.c"
void main()
{
setup_oscillator(OSC_16MHZ);
while(TRUE)
{
spi_xfer(0xAA);
delay_us(10);
}
}
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I send one byte for 25uS.
But when I use the setup_spi line in my code I get faster bit rate:
| Code: |
#include <16F1508.h>
#FUSES INTRC_IO, NOWDT, PUT, NOMCLR, NOPROTECT, NOBROWNOUT, NOCLKOUT, NOIESO, NOFCMEN, NOWRT, NOLPBOR, NODEBUG, NOLVP
#USE delay(internal = 16M)
#use spi(FORCE_HW, BITS=8, ENABLE=PIN_C6, ENABLE_ACTIVE=0)
#include "NRF24L01.c"
void main()
{
setup_oscillator(OSC_16MHZ);
setup_spi(SPI_MASTER | SPI_SCK_IDLE_LOW | SPI_XMIT_L_TO_H | SPI_SS_C6);
while(TRUE)
{
spi_xfer(0xAA);
delay_us(10);
}
}
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Now I send one byte for approximately 2uS.
Much faster with second piece of code. Could you please shed some light.
_________________
A person who never made a mistake never tried anything new. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19537
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| Posted: Sun May 10, 2015 6:48 am |
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| #use spi, allows you to specify the baud.... |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sun May 10, 2015 7:18 am |
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| Quote: | BAUD=n
Target bits per second, default is as fast as possible. |
_________________
A person who never made a mistake never tried anything new. |
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Ttelmah
Joined: 11 Mar 2010
Posts: 19537
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| Posted: Sun May 10, 2015 12:21 pm |
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If you believe that, you will believe anything..... 
You'll find it does go as fast as possible for software SPI, but for hardware, unless you specify the rate, it doesn't configure things like the prescaler. |
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rikotech8
Joined: 10 Dec 2011
Posts: 376
Location: Sofiq,Bulgariq
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| Posted: Sun May 10, 2015 1:23 pm |
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Thx a lot T
_________________
A person who never made a mistake never tried anything new. |
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