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quangphongit
Guest
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| SPI on PIC18F4580 Master and PIC16F877A Slave |
 Posted: Thu May 15, 2008 10:38 am |
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I'm trying to demo SPI interface between 18F4580 is Master and 16F877A is slave, used 4 wire: SDI, SDO, SCK and nSS.
This is my code for Master:
| Code: |
#define SS_LOW (output_low(pin_A5)) //pin RA5 conected to nSS in 16F877A
#define SS_HIGH (output_high(pin_A5))
void main()
{
byte rs;
setup_spi(SPI_MASTER|SPI_L_TO_H|SPI_CLK_DIV_4|SPI_SAMPLE_AT_END);
while(1)
{
delay_ms(3000);
SS_LOW;
spi_write(0x55);
rs = spi_read();
SS_HIGH;
led_perform(1); // led on and off in 200ms when transmitting is completed
}
}
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//And this my code for slave
| Code: | void main()
{
byte kq;
setup_spi(SPI_SLAVE);
while(1)
{
kq = spi_read();
delay_us(100);
output_d(kq); //output kq on port D
spi_write(0);
/*if(spi_data_is_in())
{
led_perform(1); //led on and off one time
if(SSPBUF==0x55)
{
led_perform(3); //led on and off three time
}
delay_ms(1000);
}*/
}
} |
I compiled this code completed, and loaded it in the PIC.
But the slave didn't receive any bit from Master, had not perform any thing (led on-off 0 time, and port D perform nothing)
Please tell me why???
Thanks guys. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu May 15, 2008 11:46 am |
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Look at the CCS example files for an SPI slave:
| Quote: | c:\Program Files\picc\Examples\Ex_spi_slave.c
c:\Program Files\picc\Examples\Ex_spi.c |
This thread has code that demonstrates an SPI slave
but it's done using one board (because it's a demonstration).
http://www.ccsinfo.com/forum/viewtopic.php?t=26888 |
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quangphongit
Guest
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| Experiented |
| Posted: Thu May 15, 2008 11:47 pm |
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My kit was run very well!
The problem is, after init the SPI interface, should add delay_ms(100) and after each spi_read() should add delay_ms(1). I tried and succeeded.
the code here
| Code: |
//MASTER
void main()
{
setup_spi(SPI_MASTER|SPI_L_TO_H|SPI_CLK_DIV_4|SPI_SAMPLE_AT_END); // TODO: USER CODE!!
delay_ms(100);
while(1)
{
SS_LOW;
rs = spi_read(0x55);
delay_ms(1);
SS_HIGH;
if(rs==0x33)
{
led_perform(1);
}
}
}
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| Code: |
void main()
{
setup_spi(SPI_SLAVE);
delay_ms(100);
while(1)
{
kq = spi_read();
delay_ms(1);
spi_write(0x33);
if(kq==0x55)
{
led_perform(1);
}
}
}
|
This code is running well, SPI transfer well.
I post this reply to show the basic transfer of SPI for who don't know this, as me yesterday.
Thanks guys |
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art
Guest
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| 2 wire SPI |
| Posted: Tue Feb 02, 2010 4:48 am |
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Has anybody implemented a 2-wire SPI in a PIC16F877A or in any microcontroller as the master? I need some info for this because my slave IC which is an energy IC is configured as 2 wire SPI. All I need is to supply serial clock from the PIC to the slave so that I can get the data. The data comes from the slave.
Is it possible that a PIC can be configured as 2 wire SPI using only the SCK and SDI pin? Will the PIC (master) still supply a serial clock if it is configured as 2 wire SPI? |
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