ODROID-C5: analog: fix for ODROID-C5

ODROID-C5 has two internal 10bit ADCs. However, the value of in_voltage0_raw outputs a difficult number.

So, klipper read "in_voltage0_input", which outputs the actual voltage value, to read the value of ADC.

The iio device file, The read speed of "in_voltage0_input" is very slow. This will adversely affect the stepper motor operation and result in a "Stepper too far in past" error.

Read the value of Voltage0_raw and calculate the ADC voltage directly in the klipper.

Change-Id: I293cbdf8d1f54efe50ab89729a9908eb598820b6

src/linux/Makefile

@@ -3,10 +3,13 @@
 dirs-y += src/linux src/generic
 
 src-y += linux/main.c linux/timer.c linux/console.c linux/watchdog.c
-src-y += linux/pca9685.c linux/spidev.c linux/analog.c linux/hard_pwm.c
+src-y += linux/pca9685.c linux/spidev.c linux/hard_pwm.c
 src-y += linux/i2c.c linux/gpio.c generic/crc16_ccitt.c generic/alloc.c
 src-y += linux/sensor_ds18b20.c
 
+src-$(CONFIG_MACH_LINUX_DEFAULT) += linux/analog.c
+src-$(CONFIG_MACH_LINUX_ODROIDC5) += linux/analog_odroidc5.c
+
 CFLAGS_klipper.elf += -lutil -lrt -lpthread
 
 flash: $(OUT)klipper.elf

src/linux/analog_odroidc5.c

@@ -0,0 +1,102 @@
+// Read analog values from Linux IIO device
+//
+// Copyright (C) 2017  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <fcntl.h> // open
+#include <stdio.h> // snprintf
+#include <stdlib.h> // atoi
+#include <unistd.h> // read
+#include "command.h" // shutdown
+#include "gpio.h" // gpio_adc_setup
+#include "internal.h" // report_errno
+#include "sched.h" // sched_shutdown
+
+// ODROID-C5
+DECL_CONSTANT("ADC_MAX", 1800);
+
+#define ANALOG_START (1<<12)
+
+DECL_ENUMERATION_RANGE("pin", "analog0", ANALOG_START, 8);
+
+// ODROID-C5
+#define IIO_PATH "/sys/bus/iio/devices/iio:device0/in_voltage0_raw"
+#define SCALE_PATH "/sys/bus/iio/devices/iio:device0/in_voltage_scale"
+#define OFFSET_PATH "/sys/bus/iio/devices/iio:device0/in_voltage_offset"
+
+struct gpio_adc
+gpio_adc_setup(uint32_t pin)
+{
+    struct gpio_adc g;
+	int fd;
+    char buf[64];
+    int ret;
+
+	fd = open(SCALE_PATH, O_RDONLY);
+    ret = read(fd, buf, sizeof(buf)-1);
+    if (ret <= 0) {
+        goto fail;
+    }
+    buf[ret] = '\0';
+    g.scale = atof(buf) * 1000;
+    close(fd);
+
+    fd = open(OFFSET_PATH, O_RDONLY);
+    ret = read(fd, buf, sizeof(buf)-1);
+    if (ret <= 0) {
+        goto fail;
+    }
+    buf[ret] = '\0';
+    g.offset = atoi(buf);
+    close(fd);
+
+    fd = open(IIO_PATH, O_RDONLY|O_CLOEXEC);
+    if (fd < 0) {
+        report_errno("analog open", fd);
+        goto fail;
+    }
+    ret = set_non_blocking(fd);
+    if (ret < 0)
+        goto fail;
+
+    g.fd = fd;
+    return g;
+fail:
+    if (fd >= 0)
+        close(fd);
+    shutdown("Unable to open adc device");
+}
+
+uint32_t
+gpio_adc_sample(struct gpio_adc g)
+{
+    return 0;
+}
+
+uint16_t
+gpio_adc_read(struct gpio_adc g)
+{
+    char buf[64];
+    int voltage;
+    int ret = pread(g.fd, buf, sizeof(buf)-1, 0);
+    if (ret <= 0) {
+        report_errno("analog read", ret);
+        try_shutdown("Error on analog read");
+        return 0;
+    }
+    buf[ret] = '\0';
+
+	voltage = atoi(buf) + g.offset;
+	voltage = voltage > 0 ? voltage : 0;
+	voltage = voltage * g.scale;
+	voltage = voltage < 1800000 ? voltage : 1800000;
+	voltage /= 1000;
+
+    return voltage;
+}
+
+void
+gpio_adc_cancel_sample(struct gpio_adc g)
+{
+}

src/linux/gpio.h

@@ -1,6 +1,7 @@
 #ifndef __LINUX_GPIO_H
 #define __LINUX_GPIO_H
 
+#include "autoconf.h" // CONFIG_MACH_LINUX_*
 #include <stdint.h> // uint8_t
 
 struct gpio_out {
@@ -20,6 +21,10 @@ void gpio_in_reset(struct gpio_in g, int8_t pull_up);
 uint8_t gpio_in_read(struct gpio_in g);
 
 struct gpio_adc {
+#ifdef CONFIG_MACH_LINUX_ODROIDC5
+    int scale;
+    int offset;
+#endif
     int fd;
 };
 struct gpio_adc gpio_adc_setup(uint32_t pin);