linux: Add support for pca9685 i2c pwm devices

Add support for controlling pca9685 PWM drivers using the standard
Linux I2C interface.  The pca9685 device is found on Replicape boards.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

1 files changed, 205 insertions, 0 deletions

diff --git a/src/linux/pca9685.c b/src/linux/pca9685.c
new file mode 100644
index 00000000..4c1611aa
--- /dev/null
+++ b/src/linux/pca9685.c
@@ -0,0 +1,205 @@
+// Communicating with a PCA9685 pwm device via linux i2c
+//
+// 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 <linux/i2c-dev.h> // I2C_SLAVE
+#include <stdio.h> // snprintf
+#include <sys/ioctl.h> // ioctl
+#include <unistd.h> // write
+#include "basecmd.h" // oid_alloc
+#include "board/misc.h" // timer_from_us
+#include "command.h" // DECL_COMMAND
+#include "internal.h" // report_errno
+#include "sched.h" // DECL_SHUTDOWN
+
+
+/****************************************************************
+ * Low-level i2c
+ ****************************************************************/
+
+#define P9_MODE1    0x00
+#define P9_PRESCALE 0xfe
+#define CHANNEL_MAX 15
+#define CHANNEL_ALL 61
+#define VALUE_MAX 4096
+
+#define OSC_MHZ   25
+#define CLOCK_MHZ timer_from_us(1)
+
+struct i2c_s {
+    uint8_t bus;
+    uint8_t addr;
+    uint32_t cycle_ticks;
+    int fd;
+};
+static struct i2c_s devices[16];
+static int devices_count;
+
+static void
+pca9685_write(int fd, uint8_t channel, uint16_t value)
+{
+    uint8_t full_on = 0x00;
+    if (value >= VALUE_MAX) {
+        full_on = 0x10;
+        value = 0x0000;
+    } else if (!value) {
+        value = 0x1000;
+    }
+    uint8_t msg[5] = { channel*4 + 0x06, 0x00, full_on, value, value >> 8 };
+    int ret = write(fd, msg, sizeof(msg));
+    if (ret < 0) {
+        report_errno("write value i2c", ret);
+        try_shutdown("Unable to update PCA9685 value");
+    }
+}
+
+static int
+open_i2c(uint8_t bus, uint8_t addr, uint32_t cycle_ticks)
+{
+    // Find existing device (if already opened)
+    int i;
+    for (i=0; i<devices_count; i++)
+        if (devices[i].bus == bus && devices[i].addr == addr) {
+            if (cycle_ticks != devices[i].cycle_ticks)
+                shutdown("All PCA9685 channels must have the same cycle_ticks");
+            return devices[i].fd;
+        }
+
+    // Setup new I2C device
+    if (devices_count >= ARRAY_SIZE(devices))
+        shutdown("Too many i2c devices");
+    char fname[256];
+    snprintf(fname, sizeof(fname), "/dev/i2c-%d", bus);
+    int fd = open(fname, O_RDWR|O_CLOEXEC);
+    if (fd < 0) {
+        report_errno("open i2c", fd);
+        shutdown("Unable to open i2c device");
+    }
+    int ret = ioctl(fd, I2C_SLAVE, addr);
+    if (ret < 0) {
+        report_errno("ioctl i2c", fd);
+        shutdown("Unable to set address on i2c device");
+    }
+    ret = set_non_blocking(fd);
+    if (ret < 0)
+        shutdown("Unable to set non-blocking on i2c device");
+
+    // Init PCA9685
+    const uint8_t sleep_msg[2] = { P9_MODE1, 0x31 };
+    ret = write(fd, sleep_msg, sizeof(sleep_msg));
+    if (ret < 0) {
+        report_errno("write sleep i2c", ret);
+        shutdown("Unable to sleep PCA9685");
+    }
+    uint32_t freq = DIV_ROUND_CLOSEST(OSC_MHZ*cycle_ticks, 4096*CLOCK_MHZ) - 1;
+    freq = freq > 0xff ? 0xff : (freq < 0x03 ? 0x03 : freq);
+    uint8_t freq_msg[2] = { P9_PRESCALE, freq };
+    ret = write(fd, freq_msg, sizeof(freq_msg));
+    if (ret < 0) {
+        report_errno("write freq i2c", ret);
+        shutdown("Unable to set freq on PCA9685");
+    }
+    const uint8_t wake_msg[2] = { P9_MODE1, 0x21 };
+    ret = write(fd, wake_msg, sizeof(wake_msg));
+    if (ret < 0) {
+        report_errno("write unsleep i2c", ret);
+        shutdown("Unable to wake PCA9685");
+    }
+    usleep(500);
+    pca9685_write(fd, CHANNEL_ALL, 0);
+
+    devices[devices_count].bus = bus;
+    devices[devices_count].addr = addr;
+    devices[devices_count].cycle_ticks = cycle_ticks;
+    devices[devices_count].fd = fd;
+    return fd;
+}
+
+void
+pca9685_shutdown(void)
+{
+    int i;
+    for (i=0; i<devices_count; i++)
+        pca9685_write(devices[i].fd, CHANNEL_ALL, 0);
+}
+DECL_SHUTDOWN(pca9685_shutdown);
+
+
+/****************************************************************
+ * Command interface
+ ****************************************************************/
+
+struct i2cpwm_s {
+    struct timer timer;
+    int fd;
+    uint8_t channel;
+    uint16_t value;
+    uint32_t max_duration;
+};
+
+DECL_CONSTANT(PCA9685_MAX, VALUE_MAX);
+
+static uint_fast8_t
+pca9685_end_event(struct timer *timer)
+{
+    shutdown("Missed scheduling of next pca9685 event");
+}
+
+static uint_fast8_t
+pca9685_event(struct timer *timer)
+{
+    struct i2cpwm_s *p = container_of(timer, struct i2cpwm_s, timer);
+    pca9685_write(p->fd, p->channel, p->value);
+    if (!p->value || !p->max_duration)
+        return SF_DONE;
+    p->timer.waketime += p->max_duration;
+    p->timer.func = pca9685_end_event;
+    return SF_RESCHEDULE;
+}
+
+void
+command_config_pca9685(uint32_t *args)
+{
+    struct i2cpwm_s *p = oid_alloc(args[0], command_config_pca9685
+                                   , sizeof(*p));
+    uint8_t bus = args[1];
+    uint8_t addr = args[2];
+    p->channel = args[3];
+    if (p->channel > CHANNEL_MAX)
+        shutdown("Invalid pca9685 channel");
+    p->max_duration = args[5];
+    p->fd = open_i2c(bus, addr, args[4]);
+}
+DECL_COMMAND(command_config_pca9685, "config_pca9685 oid=%c bus=%c addr=%c"
+             " channel=%c cycle_ticks=%u max_duration=%u");
+
+void
+command_schedule_pca9685_out(uint32_t *args)
+{
+    struct i2cpwm_s *p = oid_lookup(args[0], command_config_pca9685);
+    sched_del_timer(&p->timer);
+    p->timer.func = pca9685_event;
+    p->timer.waketime = args[1];
+    p->value = args[2];
+    if (p->value > VALUE_MAX)
+        shutdown("Invalid pca9685 value");
+    sched_add_timer(&p->timer);
+}
+DECL_COMMAND(command_schedule_pca9685_out,
+             "schedule_pca9685_out oid=%c clock=%u value=%hu");
+
+void
+command_set_pca9685_out(uint32_t *args)
+{
+    uint8_t bus = args[0], addr = args[1], channel = args[2];
+    uint16_t value = args[4];
+    if (channel > CHANNEL_MAX || value > VALUE_MAX)
+        shutdown("Invalid pca9685 channel or value");
+    int fd = open_i2c(bus, addr, args[3]);
+    pca9685_write(fd, channel, value);
+}
+DECL_COMMAND(command_set_pca9685_out, "set_pca9685_out bus=%c addr=%c"
+             " channel=%c cycle_ticks=%u value=%hu");