esp8266: Add PWM support.

PWM implementation uses a timer and interrupts (FRC1), taken from
Espressif's/NodeMCU's implementation and adapted for our use.

8 channels are supported, on pins 0, 2, 4, 5, 12, 13, 14, 15.

Usage:

    import machine
    pwm0 = machine.PWM(machine.Pin(0))
    pwm0.freq(1000)
    pwm0.duty(500)

Frequency is shared (ie the same) for all channels.  Frequency is
between 1 and 1000.  Duty is between 0 and 1023.

1 files changed, 427 insertions, 0 deletions

diff --git a/esp8266/esppwm.c b/esp8266/esppwm.c
new file mode 100644
index 0000000000..6c89caa4ba
--- /dev/null
+++ b/esp8266/esppwm.c
@@ -0,0 +1,427 @@
+/******************************************************************************
+ * Copyright 2013-2014 Espressif Systems (Wuxi)
+ *
+ * FileName: pwm.c
+ *
+ * Description: pwm driver
+ *
+ * Modification history:
+ *     2014/5/1, v1.0 create this file.
+ *     2016/3/2: Modifications by dpgeorge to suit MicroPython
+*******************************************************************************/
+#include <stdio.h>
+#include <string.h>
+
+#include "etshal.h"
+#include "os_type.h"
+#include "gpio.h"
+
+#include "esppwm.h"
+
+#include "py/mpprint.h"
+#define PWM_DBG(...)
+//#define PWM_DBG(...) mp_printf(&mp_plat_print, __VA_ARGS__)
+
+#define ICACHE_RAM_ATTR // __attribute__((section(".text")))
+
+#define PWM_CHANNEL 8
+#define PWM_DEPTH 1023
+#define PWM_FREQ_MAX 1000
+#define PWM_1S 1000000
+
+struct pwm_single_param {
+    uint16_t gpio_set;
+    uint16_t gpio_clear;
+    uint32_t h_time;
+};
+
+struct pwm_param {
+    uint32_t period;
+    uint16_t freq;
+    uint16_t duty[PWM_CHANNEL];
+};
+
+STATIC const uint8_t pin_num[PWM_CHANNEL] = {0, 2, 4, 5, 12, 13, 14, 15};
+
+STATIC struct pwm_single_param pwm_single_toggle[2][PWM_CHANNEL + 1];
+STATIC struct pwm_single_param *pwm_single;
+
+STATIC struct pwm_param pwm;
+
+STATIC int8_t pwm_out_io_num[PWM_CHANNEL] = {-1, -1, -1, -1, -1, -1, -1, -1};
+
+STATIC uint8_t pwm_channel_toggle[2];
+STATIC uint8_t *pwm_channel;
+STATIC uint8_t pwm_toggle = 1;
+STATIC uint8_t pwm_timer_down = 1;
+STATIC uint8_t pwm_current_channel = 0;
+STATIC uint16_t pwm_gpio = 0;
+STATIC uint8_t pwm_channel_num = 0;
+
+//XXX: 0xffffffff/(80000000/16)=35A
+#define US_TO_RTC_TIMER_TICKS(t)          \
+    ((t) ?                                   \
+     (((t) > 0x35A) ?                   \
+      (((t)>>2) * ((APB_CLK_FREQ>>4)/250000) + ((t)&0x3) * ((APB_CLK_FREQ>>4)/1000000))  :    \
+      (((t) *(APB_CLK_FREQ>>4)) / 1000000)) :    \
+     0)
+
+//FRC1
+#define FRC1_ENABLE_TIMER  BIT7
+
+typedef enum {
+    DIVDED_BY_1 = 0,
+    DIVDED_BY_16 = 4,
+    DIVDED_BY_256 = 8,
+} TIMER_PREDIVED_MODE;
+
+typedef enum {
+    TM_LEVEL_INT = 1,
+    TM_EDGE_INT   = 0,
+} TIMER_INT_MODE;
+
+STATIC void ICACHE_FLASH_ATTR
+pwm_insert_sort(struct pwm_single_param pwm[], uint8 n)
+{
+    uint8 i;
+
+    for (i = 1; i < n; i++) {
+        if (pwm[i].h_time < pwm[i - 1].h_time) {
+            int8 j = i - 1;
+            struct pwm_single_param tmp;
+
+            memcpy(&tmp, &pwm[i], sizeof(struct pwm_single_param));
+            memcpy(&pwm[i], &pwm[i - 1], sizeof(struct pwm_single_param));
+
+            while (tmp.h_time < pwm[j].h_time) {
+                memcpy(&pwm[j + 1], &pwm[j], sizeof(struct pwm_single_param));
+                j--;
+                if (j < 0) {
+                    break;
+                }
+            }
+
+            memcpy(&pwm[j + 1], &tmp, sizeof(struct pwm_single_param));
+        }
+    }
+}
+
+STATIC volatile uint8 critical = 0;
+
+#define LOCK_PWM(c)  do {                       \
+    while( (c)==1 );                            \
+    (c) = 1;                                    \
+} while (0)
+
+#define UNLOCK_PWM(c) do {                      \
+    (c) = 0;                                    \
+} while (0)
+
+void ICACHE_FLASH_ATTR
+pwm_start(void)
+{
+    uint8 i, j;
+    PWM_DBG("--Function pwm_start() is called\n");
+    PWM_DBG("pwm_gpio:%x,pwm_channel_num:%d\n",pwm_gpio,pwm_channel_num);
+    PWM_DBG("pwm_out_io_num[0]:%d,[1]:%d,[2]:%d\n",pwm_out_io_num[0],pwm_out_io_num[1],pwm_out_io_num[2]);
+    PWM_DBG("pwm.period:%d,pwm.duty[0]:%d,[1]:%d,[2]:%d\n",pwm.period,pwm.duty[0],pwm.duty[1],pwm.duty[2]);
+
+    LOCK_PWM(critical);   // enter critical
+
+    struct pwm_single_param *local_single = pwm_single_toggle[pwm_toggle ^ 0x01];
+    uint8 *local_channel = &pwm_channel_toggle[pwm_toggle ^ 0x01];
+
+    // step 1: init PWM_CHANNEL+1 channels param
+    for (i = 0; i < pwm_channel_num; i++) {
+        uint32 us = pwm.period * pwm.duty[i] / PWM_DEPTH;
+        local_single[i].h_time = US_TO_RTC_TIMER_TICKS(us);
+        PWM_DBG("i:%d us:%d ht:%d\n",i,us,local_single[i].h_time);
+        local_single[i].gpio_set = 0;
+        local_single[i].gpio_clear = 1 << pin_num[pwm_out_io_num[i]];
+    }
+
+    local_single[pwm_channel_num].h_time = US_TO_RTC_TIMER_TICKS(pwm.period);
+    local_single[pwm_channel_num].gpio_set = pwm_gpio;
+    local_single[pwm_channel_num].gpio_clear = 0;
+    PWM_DBG("i:%d period:%d ht:%d\n",pwm_channel_num,pwm.period,local_single[pwm_channel_num].h_time);
+    // step 2: sort, small to big
+    pwm_insert_sort(local_single, pwm_channel_num + 1);
+
+    *local_channel = pwm_channel_num + 1;
+    PWM_DBG("1channel:%d,single[0]:%d,[1]:%d,[2]:%d,[3]:%d\n",*local_channel,local_single[0].h_time,local_single[1].h_time,local_single[2].h_time,local_single[3].h_time);
+    // step 3: combine same duty channels
+    for (i = pwm_channel_num; i > 0; i--) {
+        if (local_single[i].h_time == local_single[i - 1].h_time) {
+            local_single[i - 1].gpio_set |= local_single[i].gpio_set;
+            local_single[i - 1].gpio_clear |= local_single[i].gpio_clear;
+
+            for (j = i + 1; j < *local_channel; j++) {
+                memcpy(&local_single[j - 1], &local_single[j], sizeof(struct pwm_single_param));
+            }
+
+            (*local_channel)--;
+        }
+    }
+    PWM_DBG("2channel:%d,single[0]:%d,[1]:%d,[2]:%d,[3]:%d\n",*local_channel,local_single[0].h_time,local_single[1].h_time,local_single[2].h_time,local_single[3].h_time);
+    // step 4: cacl delt time
+    for (i = *local_channel - 1; i > 0; i--) {
+        local_single[i].h_time -= local_single[i - 1].h_time;
+    }
+
+    // step 5: last channel needs to clean
+    local_single[*local_channel-1].gpio_clear = 0;
+
+    // step 6: if first channel duty is 0, remove it
+    if (local_single[0].h_time == 0) {
+        local_single[*local_channel - 1].gpio_set &= ~local_single[0].gpio_clear;
+        local_single[*local_channel - 1].gpio_clear |= local_single[0].gpio_clear;
+
+        for (i = 1; i < *local_channel; i++) {
+            memcpy(&local_single[i - 1], &local_single[i], sizeof(struct pwm_single_param));
+        }
+
+        (*local_channel)--;
+    }
+
+    // if timer is down, need to set gpio and start timer
+    if (pwm_timer_down == 1) {
+        pwm_channel = local_channel;
+        pwm_single = local_single;
+        // start
+        gpio_output_set(local_single[0].gpio_set, local_single[0].gpio_clear, pwm_gpio, 0);
+
+        // yeah, if all channels' duty is 0 or 255, don't need to start timer, otherwise start...
+        if (*local_channel != 1) {
+            pwm_timer_down = 0;
+            RTC_REG_WRITE(FRC1_LOAD_ADDRESS, local_single[0].h_time);
+        }
+    }
+
+    if (pwm_toggle == 1) {
+        pwm_toggle = 0;
+    } else {
+        pwm_toggle = 1;
+    }
+
+    UNLOCK_PWM(critical);   // leave critical
+    PWM_DBG("3channel:%d,single[0]:%d,[1]:%d,[2]:%d,[3]:%d\n",*local_channel,local_single[0].h_time,local_single[1].h_time,local_single[2].h_time,local_single[3].h_time);
+}
+
+/******************************************************************************
+ * FunctionName : pwm_set_duty
+ * Description  : set each channel's duty params
+ * Parameters   : uint8 duty    : 0 ~ PWM_DEPTH
+ *                uint8 channel : channel index
+ * Returns      : NONE
+*******************************************************************************/
+void ICACHE_FLASH_ATTR
+pwm_set_duty(uint16 duty, uint8 channel)
+{
+    uint8 i;
+    for(i=0;i<pwm_channel_num;i++){
+        if(pwm_out_io_num[i] == channel){
+            channel = i;
+            break;
+        }
+    }
+    if(i==pwm_channel_num)      // non found
+        return;
+
+    LOCK_PWM(critical);   // enter critical
+    if (duty < 1) {
+        pwm.duty[channel] = 0;
+    } else if (duty >= PWM_DEPTH) {
+        pwm.duty[channel] = PWM_DEPTH;
+    } else {
+        pwm.duty[channel] = duty;
+    }
+    UNLOCK_PWM(critical);   // leave critical
+}
+
+/******************************************************************************
+ * FunctionName : pwm_set_freq
+ * Description  : set pwm frequency
+ * Parameters   : uint16 freq : 100hz typically
+ * Returns      : NONE
+*******************************************************************************/
+void ICACHE_FLASH_ATTR
+pwm_set_freq(uint16 freq, uint8 channel)
+{
+    LOCK_PWM(critical);   // enter critical
+    if (freq > PWM_FREQ_MAX) {
+        pwm.freq = PWM_FREQ_MAX;
+    } else if (freq < 1) {
+        pwm.freq = 1;
+    } else {
+        pwm.freq = freq;
+    }
+
+    pwm.period = PWM_1S / pwm.freq;
+    UNLOCK_PWM(critical);   // leave critical
+}
+
+/******************************************************************************
+ * FunctionName : pwm_get_duty
+ * Description  : get duty of each channel
+ * Parameters   : uint8 channel : channel index
+ * Returns      : NONE
+*******************************************************************************/
+uint16 ICACHE_FLASH_ATTR
+pwm_get_duty(uint8 channel)
+{
+    uint8 i;
+    for(i=0;i<pwm_channel_num;i++){
+        if(pwm_out_io_num[i] == channel){
+            channel = i;
+            break;
+        }
+    }
+    if(i==pwm_channel_num)      // non found
+        return 0;
+
+    return pwm.duty[channel];
+}
+
+/******************************************************************************
+ * FunctionName : pwm_get_freq
+ * Description  : get pwm frequency
+ * Parameters   : NONE
+ * Returns      : uint16 : pwm frequency
+*******************************************************************************/
+uint16 ICACHE_FLASH_ATTR
+pwm_get_freq(uint8 channel)
+{
+    return pwm.freq;
+}
+
+/******************************************************************************
+ * FunctionName : pwm_period_timer
+ * Description  : pwm period timer function, output high level,
+ *                start each channel's high level timer
+ * Parameters   : NONE
+ * Returns      : NONE
+*******************************************************************************/
+STATIC void ICACHE_RAM_ATTR
+pwm_tim1_intr_handler(void)
+{
+    uint8 local_toggle = pwm_toggle;                        // pwm_toggle may change outside
+    RTC_CLR_REG_MASK(FRC1_INT_ADDRESS, FRC1_INT_CLR_MASK);
+
+    if (pwm_current_channel >= (*pwm_channel - 1)) {        // *pwm_channel may change outside
+        pwm_single = pwm_single_toggle[local_toggle];
+        pwm_channel = &pwm_channel_toggle[local_toggle];
+
+        gpio_output_set(pwm_single[*pwm_channel - 1].gpio_set,
+                        pwm_single[*pwm_channel - 1].gpio_clear,
+                        pwm_gpio,
+                        0);
+
+        pwm_current_channel = 0;
+
+        if (*pwm_channel != 1) {
+            RTC_REG_WRITE(FRC1_LOAD_ADDRESS, pwm_single[pwm_current_channel].h_time);
+        } else {
+            pwm_timer_down = 1;
+        }
+    } else {
+        gpio_output_set(pwm_single[pwm_current_channel].gpio_set,
+                        pwm_single[pwm_current_channel].gpio_clear,
+                        pwm_gpio, 0);
+
+        pwm_current_channel++;
+        RTC_REG_WRITE(FRC1_LOAD_ADDRESS, pwm_single[pwm_current_channel].h_time);
+    }
+}
+
+/******************************************************************************
+ * FunctionName : pwm_init
+ * Description  : pwm gpio, params and timer initialization
+ * Parameters   : uint16 freq : pwm freq param
+ *                uint16 *duty : each channel's duty
+ * Returns      : NONE
+*******************************************************************************/
+void ICACHE_FLASH_ATTR
+pwm_init(void)
+{
+    uint8 i;
+
+    RTC_REG_WRITE(FRC1_CTRL_ADDRESS,  //FRC2_AUTO_RELOAD|
+                  DIVDED_BY_16
+                  | FRC1_ENABLE_TIMER
+                  | TM_EDGE_INT);
+    RTC_REG_WRITE(FRC1_LOAD_ADDRESS, 0);
+
+    for (i = 0; i < PWM_CHANNEL; i++) {
+        pwm_gpio = 0;
+        pwm.duty[i] = 0;
+    }
+
+    pwm_set_freq(500, 0);
+    pwm_start();
+
+    ETS_FRC_TIMER1_INTR_ATTACH(pwm_tim1_intr_handler, NULL);
+    TM1_EDGE_INT_ENABLE();
+    ETS_FRC1_INTR_ENABLE();
+}
+
+int ICACHE_FLASH_ATTR
+pwm_add(uint8_t pin_id, uint32_t pin_mux, uint32_t pin_func){
+    PWM_DBG("--Function pwm_add() is called. channel:%d\n", channel);
+    PWM_DBG("pwm_gpio:%x,pwm_channel_num:%d\n",pwm_gpio,pwm_channel_num);
+    PWM_DBG("pwm_out_io_num[0]:%d,[1]:%d,[2]:%d\n",pwm_out_io_num[0],pwm_out_io_num[1],pwm_out_io_num[2]);
+    PWM_DBG("pwm.duty[0]:%d,[1]:%d,[2]:%d\n",pwm.duty[0],pwm.duty[1],pwm.duty[2]);
+    int channel = -1;
+    for (int i = 0; i < PWM_CHANNEL; ++i) {
+        if (pin_num[i] == pin_id) {
+            channel = i;
+            break;
+        }
+    }
+    if (channel == -1) {
+        return -1;
+    }
+    uint8 i;
+    for(i=0;i<PWM_CHANNEL;i++){
+        if(pwm_out_io_num[i]==channel)  // already exist
+            return channel;
+        if(pwm_out_io_num[i] == -1){ // empty exist
+            LOCK_PWM(critical);   // enter critical
+            pwm_out_io_num[i] = channel;
+            pwm.duty[i] = 0;
+            pwm_gpio |= (1 << pin_num[channel]);
+            PIN_FUNC_SELECT(pin_mux, pin_func);
+            GPIO_REG_WRITE(GPIO_PIN_ADDR(GPIO_ID_PIN(pin_num[channel])), GPIO_REG_READ(GPIO_PIN_ADDR(GPIO_ID_PIN(pin_num[channel]))) & (~ GPIO_PIN_PAD_DRIVER_SET(GPIO_PAD_DRIVER_ENABLE))); //disable open drain;
+            pwm_channel_num++;
+            UNLOCK_PWM(critical);   // leave critical
+            return channel;
+        }
+    }
+    return -1;
+}
+
+bool ICACHE_FLASH_ATTR
+pwm_delete(uint8 channel){
+    PWM_DBG("--Function pwm_delete() is called. channel:%d\n", channel);
+    PWM_DBG("pwm_gpio:%x,pwm_channel_num:%d\n",pwm_gpio,pwm_channel_num);
+    PWM_DBG("pwm_out_io_num[0]:%d,[1]:%d,[2]:%d\n",pwm_out_io_num[0],pwm_out_io_num[1],pwm_out_io_num[2]);
+    PWM_DBG("pwm.duty[0]:%d,[1]:%d,[2]:%d\n",pwm.duty[0],pwm.duty[1],pwm.duty[2]);
+    uint8 i,j;
+    for(i=0;i<pwm_channel_num;i++){
+        if(pwm_out_io_num[i]==channel){  // exist
+            LOCK_PWM(critical);   // enter critical
+            pwm_out_io_num[i] = -1;
+            pwm_gpio &= ~(1 << pin_num[channel]);   //clear the bit
+            for(j=i;j<pwm_channel_num-1;j++){
+                pwm_out_io_num[j] = pwm_out_io_num[j+1];
+                pwm.duty[j] = pwm.duty[j+1];
+            }
+            pwm_out_io_num[pwm_channel_num-1] = -1;
+            pwm.duty[pwm_channel_num-1] = 0;
+            pwm_channel_num--;
+            UNLOCK_PWM(critical);   // leave critical
+            return true;
+        }
+    }
+    // non found
+    return true;
+}