178 lines
5.4 KiB
C
178 lines
5.4 KiB
C
//
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// Simple byte wise SPI driver
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// Demo how to set up memmap and access SPI registers.
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// Code seems to be working but has not been much tested.
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// G.J. van Loo 15-Jan-2012
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//
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// Access from ARM Running Linux
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#define BCM2708_PERI_BASE 0x20000000
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#define UART0_BASE (BCM2708_PERI_BASE + 0x201000) /* Uart 0 */
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#define UART1_BASE (BCM2708_PERI_BASE + 0x215000) /* Uart 1 */
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#define MCORE_BASE (BCM2708_PERI_BASE + 0x0000) /* Fake frame buffer device */
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#define GPIO_BASE (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
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#define SPI0_BASE (BCM2708_PERI_BASE + 0x204000) /* SPI0 controller */
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <dirent.h>
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#include <fcntl.h>
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#include <assert.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#define PAGE_SIZE (4*1024)
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#define BLOCK_SIZE (4*1024)
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int mem_fd;
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char *gpio_mem, *gpio_map;
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char *spi0_mem, *spi0_map;
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// I/O access
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volatile unsigned *gpio;
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volatile unsigned *spi0;
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// SPI operation
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// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
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#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
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#define OUT_GPIO(g) *(gpio+((g)/10)) |= (1<<(((g)%10)*3))
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#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
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//
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#define SPI0_CNTLSTAT *(spi0 + 0)
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#define SPI0_FIFO *(spi0 + 1)
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#define SPI0_CLKSPEED *(spi0 + 2)
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// SPI0_CNTLSTAT register bits
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#define SPI0_CS_CS2ACTHIGH 0x00800000 // CS2 active high
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#define SPI0_CS_CS1ACTHIGH 0x00400000 // CS1 active high
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#define SPI0_CS_CS0ACTHIGH 0x00200000 // CS0 active high
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#define SPI0_CS_RXFIFOFULL 0x00100000 // Receive FIFO full
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#define SPI0_CS_RXFIFO3_4 0x00080000 // Receive FIFO 3/4 full
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#define SPI0_CS_TXFIFOSPCE 0x00040000 // Transmit FIFO has space
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#define SPI0_CS_RXFIFODATA 0x00020000 // Receive FIFO has data
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#define SPI0_CS_DONE 0x00010000 // SPI transfer done. WRT to CLR!
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#define SPI0_CS_MOSI_INPUT 0x00001000 // MOSI is input, read from MOSI (BI-dir mode)
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#define SPI0_CS_DEASRT_CS 0x00000800 // De-assert CS at end
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#define SPI0_CS_RX_IRQ 0x00000400 // Receive irq enable
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#define SPI0_CS_DONE_IRQ 0x00000200 // irq when done
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#define SPI0_CS_DMA_ENABLE 0x00000100 // Run in DMA mode
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#define SPI0_CS_ACTIVATE 0x00000080 // Activate: be high before starting
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#define SPI0_CS_CS_POLARIT 0x00000040 // Chip selects active high
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#define SPI0_CS_CLRTXFIFO 0x00000020 // Clear TX FIFO (auto clear bit)
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#define SPI0_CS_CLRRXFIFO 0x00000010 // Clear RX FIFO (auto clear bit)
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#define SPI0_CS_CLRFIFOS 0x00000030 // Clear BOTH FIFOs (auto clear bit)
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#define SPI0_CS_CLK_IDLHI 0x00000008 // Clock pin is high when idle
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#define SPI0_CS_CLKTRANS 0x00000004 // 0=first clock in middle of data bit
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// 1=first clock at begin of data bit
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#define SPI0_CS_CHIPSEL0 0x00000000 // Use chip select 0
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#define SPI0_CS_CHIPSEL1 0x00000001 // Use chip select 1
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#define SPI0_CS_CHIPSEL2 0x00000002 // Use chip select 2
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#define SPI0_CS_CHIPSELN 0x00000003 // No chip select (e.g. use GPIO pin)
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#define SPI0_CS_CLRALL (SPI0_CS_CLRFIFOS|SPI0_CS_DONE)
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#define ISASC(x) ((x)>=0x20 && (x)<=0x7F)
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void setup_io();
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int main(int argc, char **argv)
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{ int g;
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setup_io(); // Set up direct access to I/O for GPIO and SPI
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// Switch GPIO 7..11 to SPI mode (ALT function 0)
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/************************************************************************\
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* You are about to change the GPIO settings of your computer. *
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* Mess this up and it will stop working! *
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* It might be a good idea to 'sync' before running this program *
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* so at least you still have your code changes written to the SD-card! *
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\************************************************************************/
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for (g=7; g<=11; g++)
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{
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INP_GPIO(g); // clear bits (= input)
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SET_GPIO_ALT(g,0); // set function 0
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}
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return 0;
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} // main
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//
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// Set up a memory regions to access GPIO and SPI0
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//
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void setup_io()
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{
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/* open /dev/mem */
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if ((mem_fd = open("/dev/mem", O_RDWR|O_SYNC) ) < 0) {
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printf("can't open /dev/mem \n");
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exit (-1);
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}
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/* mmap GPIO */
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if ((gpio_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
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printf("allocation error \n");
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exit (-1);
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}
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if ((unsigned long)gpio_mem % PAGE_SIZE)
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gpio_mem += PAGE_SIZE - ((unsigned long)gpio_mem % PAGE_SIZE);
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gpio_map = (unsigned char *)mmap(
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(caddr_t)gpio_mem,
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BLOCK_SIZE,
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PROT_READ|PROT_WRITE,
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MAP_SHARED|MAP_FIXED,
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mem_fd,
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GPIO_BASE
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);
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if ((long)gpio_map < 0) {
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printf("mmap error %ld\n", (long)gpio_map);
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exit (-1);
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}
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gpio = (volatile unsigned *)gpio_map;
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/* mmap SPI0 */
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if ((spi0_mem = malloc(BLOCK_SIZE + (PAGE_SIZE-1))) == NULL) {
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printf("allocation error \n");
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exit (-1);
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}
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if ((unsigned long)spi0_mem % PAGE_SIZE)
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spi0_mem += PAGE_SIZE - ((unsigned long)spi0_mem % PAGE_SIZE);
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spi0_map = (unsigned char *)mmap(
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(caddr_t)spi0_mem,
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BLOCK_SIZE,
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PROT_READ|PROT_WRITE,
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MAP_SHARED|MAP_FIXED,
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mem_fd,
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SPI0_BASE
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);
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printf("SPI mapped from 0x%d to 0x%p\n",SPI0_BASE,spi0_map);
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if ((long)spi0_map < 0) {
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printf("mmap error %ld\n", (long)spi0_map);
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exit (-1);
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}
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spi0 = (volatile unsigned *)spi0_map;
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} // setup_io
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