Add vu peak callback.

app/modules/pcm.c

@@ -36,6 +36,7 @@ static int pcm_drv_free( lua_State *L )
   UNREF_CB( cfg->cb_drained_ref );
   UNREF_CB( cfg->cb_paused_ref );
   UNREF_CB( cfg->cb_stopped_ref );
+  UNREF_CB( cfg->cb_vu_ref );
   UNREF_CB( cfg->self_ref );
 
   if (cfg->bufs[0].data) {
@@ -160,6 +161,13 @@ static int pcm_drv_on( lua_State *L )
   } else if ((len == 7) && (c_strcmp( event, "stopped" ) == 0)) {
     luaL_unref( L, LUA_REGISTRYINDEX, cfg->cb_stopped_ref);
     cfg->cb_stopped_ref = COND_REF( is_func );
+  } else if ((len == 2) && (c_strcmp( event, "vu" ) == 0)) {
+    luaL_unref( L, LUA_REGISTRYINDEX, cfg->cb_vu_ref);
+    cfg->cb_vu_ref = COND_REF( is_func );
+
+    int freq = luaL_optinteger( L, 4, 10 );
+    luaL_argcheck( L, (freq > 0) && (freq <= 200), 4, "invalid range" );
+    cfg->vu_freq = (uint8_t)freq;
   } else {
     if (is_func) {
       // need to pop pushed function arg
@@ -187,13 +195,15 @@ static int pcm_new( lua_State *L )
   cfg->self_ref      = LUA_NOREF;
   cfg->cb_data_ref   = cfg->cb_drained_ref = LUA_NOREF;
   cfg->cb_paused_ref = cfg->cb_stopped_ref = LUA_NOREF;
+  cfg->cb_vu_ref     = LUA_NOREF;
 
   cfg->bufs[0].buf_size = cfg->bufs[1].buf_size = 0;
   cfg->bufs[0].data     = cfg->bufs[1].data     = NULL;
   cfg->bufs[0].len      = cfg->bufs[1].len      = 0;
   cfg->bufs[0].rpos     = cfg->bufs[1].rpos     = 0;
   cfg->bufs[0].empty    = cfg->bufs[1].empty    = TRUE;
 
+  cfg->data_vu_task    = task_get_id( pcm_data_vu_task );
   cfg->data_play_task  = task_get_id( pcm_data_play_task );
   cfg->start_play_task = task_get_id( pcm_start_play_task );
 

app/pcm/drv_sigma_delta.c

@@ -22,8 +22,23 @@ static void ICACHE_RAM_ATTR drv_sd_timer_isr( os_param_t arg )
   }
 
   if (!buf->empty) {
+    uint16_t tmp;
     // buffer is not empty, continue reading
 
+    tmp = abs((int16_t)(buf->data[buf->rpos]) - 128);
+    if (tmp > cfg->vu_peak_tmp) {
+      cfg->vu_peak_tmp = tmp;
+    }
+    cfg->vu_samples_tmp++;
+    if (cfg->vu_samples_tmp >= cfg->vu_req_samples) {
+      cfg->vu_peak = cfg->vu_peak_tmp;
+
+      task_post_low( cfg->data_vu_task, (os_param_t)cfg );
+
+      cfg->vu_samples_tmp = 0;
+      cfg->vu_peak_tmp    = 0;
+    }
+
     platform_sigma_delta_set_target( buf->data[buf->rpos++] );
     if (buf->rpos >= buf->len) {
       // buffer data consumed, request to re-fill it
@@ -64,6 +79,11 @@ static uint8_t drv_sd_close( cfg_t *cfg )
 
 static uint8_t drv_sd_play( cfg_t *cfg )
 {
+  // VU control: derive callback frequency
+  cfg->vu_req_samples = (uint16_t)((1000000L / (uint32_t)cfg->vu_freq) / (uint32_t)pcm_rate_def[cfg->rate]);
+  cfg->vu_samples_tmp = 0;
+  cfg->vu_peak_tmp    = 0;
+
   // (re)start hardware timer ISR to feed the sigma-delta
   if (platform_hw_timer_init( drv_sd_hw_timer_owner, FRC1_SOURCE, TRUE )) {
     platform_hw_timer_set_func( drv_sd_hw_timer_owner, drv_sd_timer_isr, (os_param_t)cfg );

app/pcm/pcm.h

@@ -64,12 +64,16 @@ typedef struct {
   uint8_t rbuf_idx;   // read by ISR
   uint8_t fbuf_idx;   // fill by data task
   // task handles
-  task_handle_t data_play_task, start_play_task;
+  task_handle_t data_vu_task, data_play_task, start_play_task;
   // callback fn refs
   int self_ref;
-  int cb_data_ref, cb_drained_ref, cb_paused_ref, cb_stopped_ref;
+    int cb_data_ref, cb_drained_ref, cb_paused_ref, cb_stopped_ref, cb_vu_ref;
   // data buffers
   pcm_buf_t bufs[2];
+  // vu measuring
+  uint8_t  vu_freq;
+  uint16_t vu_req_samples, vu_samples_tmp;
+  uint16_t vu_peak_tmp, vu_peak;
   // sigma-delta: output pin
   int pin;
 } cfg_t;
@@ -91,6 +95,7 @@ typedef struct {
 } pud_t;
 
 
+void pcm_data_vu_task( task_param_t param, uint8 prio );
 void pcm_data_play_task( task_param_t param, uint8 prio );
 
 #endif /* _PCM_H */

app/pcm/pcm_core.c

@@ -27,6 +27,19 @@ static void dispatch_callback( lua_State *L, int self_ref, int cb_ref, int retur
   }
 }
 
+void pcm_data_vu_task( task_param_t param, uint8 prio )
+{
+  cfg_t *cfg = (cfg_t *)param;
+  lua_State *L = lua_getstate();
+
+  if (cfg->cb_vu_ref != LUA_NOREF) {
+    lua_rawgeti( L, LUA_REGISTRYINDEX, cfg->cb_vu_ref );
+    lua_rawgeti( L, LUA_REGISTRYINDEX, cfg->self_ref );
+    lua_pushnumber( L, (LUA_NUMBER)(cfg->vu_peak) );
+    lua_call( L, 2, 0 );
+  }
+}
+
 void pcm_data_play_task( task_param_t param, uint8 prio )
 {
   cfg_t *cfg = (cfg_t *)param;

docs/en/modules/pcm.md

@@ -61,15 +61,16 @@ none
 Register callback functions for events.
 
 #### Syntax
-`drv:on(event[, cb_fn])`
+`drv:on(event[, cb_fn[, freq]])`
 
 #### Parameters
 - `event` identifier, one of:
   - `data` callback function is supposed to return a string containing the next chunk of data.
   - `drained` playback was stopped due to lack of data. The last 2 invocations of the `data` callback didn't provide new chunks in time (intentionally or unintentionally) and the internal buffers were fully consumed.
   - `paused` playback was paused by `pcm.drv:pause()`.
   - `stopped` playback was stopped by `pcm.drv:stop()`.
-- `cb_fn` callback function for the specified event. Unregisters previous function if omitted.
+  - `vu` new peak data, `cb_fn` is triggered `freq` times per second (1 to 200 Hz).
+- `cb_fn` callback function for the specified event. Unregisters previous function if omitted. First parameter is `drv`, followed by peak data for `vu` callback.
 
 #### Returns
 `nil`

lua_examples/pcm/play_network.lua

@@ -139,6 +139,10 @@ function M.init(pin)
   --_drv:on("stopped", cb_stopped)
 end
 
+function M.vu(cb, freq)
+ _drv:on("vu", cb, freq)
+end
+
 function M.close()
   stop_stream()
   _drv:close()