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Read the input of MCP23S17 - Pic24f

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joseph20480

Joined: 21 Dec 2011
Posts: 42

Read the input of MCP23S17 - Pic24f

Posted: Wed Sep 12, 2012 12:56 pm

HI,

I'm working on a library for my project and i have a problem...
I'm trying to set the 16 I/O in input mode, and read them but nothing (Mode output no problem).

CCS : 4.128 / Pic 24Fj64GA104

Register and pinout :

Code:

//-- MCP23S17 --
#pin_select SCK1OUT = PIN_C5 // Clock
#pin_select SDI1 = PIN_C3 // Data input
#pin_select SDO1    = PIN_c4 // Data output
#define    mcp_clk pin_c5
#define    mcp_sdi pin_c3
#define    mcp_sdo pin_c4
#define    mcp_cs pin_a4

#define write_mode 0x40
#define read_mode 0x41

#define IOCON_reg 0x0A
#define IODIR_reg 0x00 // Direction register       [ 1=input / 0=output ]
#define IPOL_reg 0x02 // Input polarity          [ 0= same / 1=opposite ]
#define GPPU_reg 0x0c // Pull up resistor register [ 1=pullup enable / 0=pullup disable ]
#define GPIO_reg 0x12 // General purpose IO register
#define OLAT_reg 0x14 // Output latch register    [ 1=logic_high / 0=logic_low ]
#define GPINTEN_reg 0x04 // Interrupt register       [ 1=enable / 0=disable]

My init function

Code:

void mcp_init()
{
setup_spi(SPI_MASTER |SPI_L_TO_H | SPI_CLK_DIV_6); // Spi n°1 - Max 10Mhz

   mcp_write(IOCON_reg,0x40,0x40); // config registre mode de communiquation

// PortA & PortB en output
      //mcp_write(IODIR_reg,0x00,0x00);
   //mcp_write(OLAT_reg,0x00,0x00);
   //mcp_write(GPPU_reg,0x00,0x00);
   //mcp_write(GPIO_reg,0xff,0xff);

// PortA & PortB en input
   mcp_write(IODIR_reg,0xFF,0xFF);    // PortA et PortB en entrees
   mcp_write(IPOL_reg,0x00,0x00);    // valeur identique a l'etat de l'input
   mcp_write(GPINTEN_reg,0x00,0x00); // Pas d'interruption

}

My Write / read function

Code:

//---------------------------------------------
void mcp_write(int8 adresse,int8 data_1,int8 data_2)
{
output_low(mcp_cs);
   spi_write(write_mode);
   spi_write(adresse);
   spi_write(data_1);
   spi_write(data_2);
output_high(mcp_cs);
}
//----------------------------------------------
void mcp_read(int8 adresse)
{
int8 data1;
int8 data2;

output_low(mcp_cs);
   spi_write(read_mode);
   spi_write(adresse);
   data1=spi_read(0);
   data2=spi_read(0);
output_high(mcp_cs);
}
//----------------------------------------------

For read my input, I call the the function mcp_read() with GPIO_reg parameter.

If someone sees a terrible mistake !?

PCM programmer

Joined: 06 Sep 2003
Posts: 21708

Posted: Wed Sep 12, 2012 4:37 pm

Quote:

setup_spi(SPI_MASTER |SPI_L_TO_H | SPI_CLK_DIV_6); // Spi n°1 - Max 10Mhz

Look at the SPI mode #define statements for the PIC24FJ-series by FvM
at the end of this thread:
http://www.ccsinfo.com/forum/viewtopic.php?t=38491&start=34

Look at Figure 2-5 in the MCP23S17 data sheet, on page 32:
http://ww1.microchip.com/downloads/en/DeviceDoc/21952b.pdf
It shows that SPI mode 0,0 or mode 1,1 can be used with this chip.

I don't know what mode you have in your setup_spi() statement. But
you need to fix it, according to the two links I gave above.

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