gpio driver

inc/gpio.h

@@ -7,8 +7,8 @@ struct gpio {
 
 int gpio_open(const struct gpio *gpio);
 int gpio_close(const struct gpio *gpio);
-char gpio_read(const struct gpio *gpio);
-void gpio_write(const struct gpio *gpio, char byte);
+int gpio_read(const struct gpio *gpio, unsigned int *value);
+int gpio_write(const struct gpio *gpio, unsigned int value);
 void gpio_toggle(const struct gpio *gpio);
 
 #endif

src/gpio.c

@@ -5,58 +5,153 @@
 
 #include <gpio.h>
 
-struct gpio_obj {
+struct ftdi_obj {
     struct ftdi_context *ftdi;
     bool is_open;
+    unsigned int vendor_id;
+    unsigned int product_id;
+    unsigned char bit_mask;
 };
 
-static struct gpio_obj gpio_obj = {
+static struct ftdi_obj ftdi_obj = {
     .ftdi = NULL,
     .is_open = false,
+    .vendor_id = 0x0403,
+    .product_id = 0x6001,
+    .bit_mask = 0,
 };
 
+static int ftdi_open(void)
+{
+    int res;
+
+    if((ftdi_obj.ftdi = ftdi_new()) == 0) {
+        syslog(LOG_ERR, "ftdi_new failed\n");
+        return EXIT_FAILURE;
+    }
+
+    res = ftdi_usb_open(ftdi_obj.ftdi, ftdi_obj.vendor_id, ftdi_obj.product_id);
+    if (res < 0 && res != -5) {
+        syslog(LOG_ERR, "unable to open ftdi device: %d (%s)\n", res,
+               ftdi_get_error_string(ftdi_obj.ftdi));
+        ftdi_free(ftdi_obj.ftdi);
+        return EXIT_FAILURE;
+    }
+
+    return EXIT_SUCCESS;
+}
+
 int gpio_open(const struct gpio *gpio)
 {
     int res;
-    if((gpio_obj.ftdi = ftdi_new()) == 0) {
-        syslog(LOG_ERR, "ftdi_new failed\n");
-        return EXIT_FAILURE;
-    }
-    res = ftdi_usb_open(gpio_obj.ftdi, 0x0403, 0x6001);
-    if (res < 0 && res != -5) {
-        syslog(LOG_ERR, "unable to open ftdi device: %d (%s)\n", res,
-               ftdi_get_error_string(gpio_obj.ftdi));
-        ftdi_free(gpio_obj.ftdi);
+    unsigned char init_value = 0;
+    bool init_write = false;
+
+
+    if(NULL == gpio) {
+        syslog(LOG_ERR, "No valid gpio object given.\n");
         return EXIT_FAILURE;
     }
 
-    res = ftdi_set_bitmode(gpio_obj.ftdi, (char)gpio->pin, BITMODE_BITBANG);
-    if(res < 0) {
-        syslog(LOG_ERR, "unable to set bit bang mode: %d (%s)\n", res,
-               ftdi_get_error_string(gpio_obj.ftdi));
-        ftdi_free(gpio_obj.ftdi);
+    if(!ftdi_obj.is_open) {
+        res = ftdi_open();
+        if(res != EXIT_SUCCESS) {
             return EXIT_FAILURE;
         }
-    gpio_obj.is_open = true;
+        init_write = true;
+    }
+
+    ftdi_obj.bit_mask |= (unsigned char)gpio->pin;
+    res = ftdi_set_bitmode(ftdi_obj.ftdi, ftdi_obj.bit_mask, BITMODE_BITBANG);
+    if(res < 0) {
+        syslog(LOG_ERR, "unable to set bit bang mode: %d (%s)\n", res,
+               ftdi_get_error_string(ftdi_obj.ftdi));
+        ftdi_free(ftdi_obj.ftdi);
+        return EXIT_FAILURE;
+    }
+    ftdi_obj.is_open = true;
+
+    if(init_write) {
+        ftdi_write_data(ftdi_obj.ftdi, &init_value, 1);
+    }
 
     return EXIT_SUCCESS;
 }
 
 int gpio_close(const struct gpio *gpio)
 {
-    ftdi_usb_close(gpio_obj.ftdi);
-    ftdi_free(gpio_obj.ftdi);
+    if(NULL == gpio) {
+        return EXIT_FAILURE;
+    }
+
+    unsigned char pin = (unsigned char)gpio->pin;
+    ftdi_obj.bit_mask &= ~pin;
+    if(ftdi_obj.bit_mask == 0) {
+        ftdi_usb_close(ftdi_obj.ftdi);
+        ftdi_free(ftdi_obj.ftdi);
+    }
 
     return EXIT_SUCCESS;
 }
 
-char gpio_read(const struct gpio *gpio)
+int gpio_read(const struct gpio *gpio, unsigned int *value)
 {
-    return 0;
+    int res;
+    unsigned char buf;
+
+    if(NULL == gpio || NULL == value) {
+        return EXIT_FAILURE;
     }
 
-void gpio_write(const struct gpio *gpio, char byte)
+    res = ftdi_read_data(ftdi_obj.ftdi, &buf, 1);
+    if(res < 0) {
+        syslog(LOG_ERR, "unable to readfrom ftdi device: %d (%s)\n", res,
+               ftdi_get_error_string(ftdi_obj.ftdi));
+        return EXIT_FAILURE;
+    }
+
+    if(buf & (unsigned char)(gpio->pin)) {
+        *value = 1;
+    } else {
+        *value = 0;
+    }
+
+    return EXIT_SUCCESS;
+}
+
+int gpio_write(const struct gpio *gpio, unsigned int value)
 {
+    int res;
+    unsigned int current_state;
+    unsigned char buf;
+
+    if(NULL == gpio) {
+        return EXIT_FAILURE;
+    }
+
+    res = gpio_read(gpio, &current_state);
+    if(res != EXIT_SUCCESS) {
+        syslog(LOG_ERR, "write failed for 0x%x, error %d (%s)\n", value, res,
+               ftdi_get_error_string(ftdi_obj.ftdi));
+        return EXIT_FAILURE;
+    }
+
+    buf = (unsigned char)current_state;
+    if(value == 0) {
+        buf &= ~(unsigned char)(gpio->pin);
+    }
+    else {
+        buf |= (unsigned char)(gpio->pin);
+    }
+
+    res = ftdi_write_data(ftdi_obj.ftdi, &buf, 1);
+    if(res < 0) {
+        syslog(LOG_ERR, "write failed for 0x%x, error %d (%s)\n", value, res,
+               ftdi_get_error_string(ftdi_obj.ftdi));
+        return EXIT_FAILURE;
+    }
+
+    return EXIT_SUCCESS;
 }
 
 void gpio_toggle(const struct gpio *gpio)

src/main.c

@@ -1,56 +1,44 @@
+#include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 #include <syslog.h>
-#include <ftdi.h>
 
-#define LED 0x08
+#include <gpio.h>
+
+const struct gpio gpio = {
+    .pin = 0x08,
+};
+
 int main(int argc, char *argv[])
 {
-    struct ftdi_context *ftdi;
-    int f, retval, cnt;
-    unsigned char buf[1];
+    int res;
+    unsigned int value;
 
     openlog("ftdi_gpio", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL1);
-    setlogmask(LOG_DEBUG);
+    // setlogmask(LOG_DEBUG);
 
-    if ((ftdi = ftdi_new()) == 0) {
-        syslog(LOG_ERR, "ftdi_new failed\n");
-        return EXIT_FAILURE;
+    res = gpio_open(&gpio);
+    if(res != EXIT_SUCCESS) {
+        syslog(LOG_ERR, "Unable to open gpio pin %u\n", gpio.pin);
+        return res;
     }
 
-    f = ftdi_usb_open(ftdi, 0x0403, 0x6001);
-
-    if (f < 0 && f != -5) {
-        syslog(LOG_ERR, "unable to open ftdi device: %d (%s)\n", f, ftdi_get_error_string(ftdi));
-        retval = 1;
-        goto done;
+    res = gpio_write(&gpio, 0x00);
+    if(res != EXIT_SUCCESS) {
+        syslog(LOG_ERR, "Unable to write to gpio pin %u\n", gpio.pin);
+        gpio_close(&gpio);
+        return res;
     }
 
-    f = ftdi_set_bitmode(ftdi, LED, BITMODE_BITBANG);
-    if(f < 0) {
-        syslog(LOG_ERR, "unable to set bit bang mode: %d (%s)\n", f, ftdi_get_error_string(ftdi));
-        retval = 1;
-        goto done;
+    res = gpio_read(&gpio, &value);
+    if(res != EXIT_SUCCESS) {
+        syslog(LOG_ERR, "Unable to read from gpio pin %u\n", gpio.pin);
+        gpio_close(&gpio);
+        return res;
     }
+    printf("read value: 0x%02x\n", value);
 
-    buf[0] = 0;
-    for(cnt = 0; cnt < 10; cnt++) {
-        buf[0] ^= LED,
-        f = ftdi_write_data(ftdi, buf, 1);
-        if(f < 0) {
-            syslog(LOG_ERR, "write failed for 0x%x, error %d (%s)\n",buf[0], f, ftdi_get_error_string(ftdi));
-            cnt = 10;
-        } else {
-            syslog(LOG_DEBUG, "set LED to: %u\n", (unsigned int)buf[0]);
-        }
-        
-        sleep(1);
-    }
-
-    ftdi_usb_close(ftdi);
-done:
-    ftdi_free(ftdi);
-    closelog();
-
-    return retval;
+    gpio_close(&gpio);
+
+    return EXIT_SUCCESS;
 }