System buffer-free version of ADC should now work. Doing so, saves about 1kb

of flash space.

NOTE: getsamples function is disabled since this is dependant on having a
buffer to get more than one sample.

Side note: single sampling without the buffer is faster by about 5-10
us/channel.  It should be possible to sidestep the buffer in certain
situations for buffer enabled mode and get a similar benefit at the cost of
some additional complexity.

inc/elua_adc.h

@@ -11,7 +11,8 @@ typedef struct
   volatile u8     op_pending: 1, // Is there a pending conversion?
                   blocking: 1, // Are we in blocking or non-blocking mode? (0 - blocking, 1 - nonblocking)
                   freerunning: 1, // If true, we don't stop when we've acquired the requested number of samples
-                  smooth_ready: 1; // Has smoothing filter warmed up (i.e. smoothlen samples collected)
+                  smooth_ready: 1, // Has smoothing filter warmed up (i.e. smoothlen samples collected)
+                  value_fresh: 1; // Whether the value pointed to by value_ptr is fresh
                     
   unsigned        id;
 

src/elua_adc.c

@@ -69,8 +69,9 @@ int adc_setup_channel( unsigned id, u8 logcount )
 {
   elua_adc_ch_state *s = adc_get_ch_state( id );
   elua_adc_dev_state *d = adc_get_dev_state( 0 );
+#if defined( BUF_ENABLE_ADC )
   int res;
-  
+
   platform_cpu_disable_interrupts();
   if( ( (u16) 1 << logcount ) != buf_get_size( BUF_ID_ADC, id ) )
   {   
@@ -79,7 +80,8 @@ int adc_setup_channel( unsigned id, u8 logcount )
       return res;
     buf_flush( BUF_ID_ADC, id );
   }
-  
+#endif
+
   s->reqsamples = (u16) 1 << logcount;
   s->op_pending = 1;
   
@@ -192,9 +194,13 @@ void adc_smooth_data( unsigned id )
   if ( s->smooth_ready == 1 )
     buf_read( BUF_ID_ADC, id, ( t_buf_data* )&sample );
   else
+  {
     sample = *( s->value_ptr );
+    s->value_fresh = 0;
+  }
 #else
   sample = *( s->value_ptr );
+  s->value_fresh = 0;
 #endif
   s->smoothbuf[ s->smoothidx ] = sample;
 
@@ -237,9 +243,16 @@ u16 adc_get_processed_sample( unsigned id )
     else if ( s->logsmoothlen == 0 )
     {
 #if defined( BUF_ENABLE_ADC )
-      buf_read( BUF_ID_ADC, id, ( t_buf_data* )&sample );
+      if( adc_samples_available( id ) == 1 )
+      {
+        sample = *( s->value_ptr ); // Don't hit buffer if only one sample is available
+        s->value_fresh = 0;
+      }
+      else
+        buf_read( BUF_ID_ADC, id, ( t_buf_data* )&sample );
 #else
       sample = *( s->value_ptr );
+      s->value_fresh = 0;
 #endif
       if ( s->reqsamples > 0)
         s->reqsamples -- ;
@@ -272,10 +285,13 @@ u16 adc_samples_requested( unsigned id )
 // Return count of available samples in the buffer
 u16 adc_samples_available( unsigned id ) 
 {
+elua_adc_ch_state *s = adc_get_ch_state( id );
+
 #if defined( BUF_ENABLE_ADC )
-  return ( u16 ) buf_get_count( BUF_ID_ADC, id );
+  u16 buffer_count = ( u16 )buf_get_count( BUF_ID_ADC, id );
+  return ( ( buffer_count == 0 ) ? s->value_fresh : buffer_count );
 #else
-  return 1; // FIXME: should keep track of whether single sample is fresh
+  return s->value_fresh;
 #endif
 }
 

src/modules/adc.c

@@ -159,7 +159,7 @@ static int adc_getsample( lua_State* L )
   return 0;
 }
 
-
+#if defined( BUF_ENABLE_ADC )
 // Lua: table_of_vals = getsamples( id, [count] )
 static int adc_getsamples( lua_State* L )
 {
@@ -193,7 +193,7 @@ static int adc_getsamples( lua_State* L )
   }
   return 1;
 }
-
+#endif
 
 // Module function map
 #define MIN_OPT_LEVEL 2
@@ -207,8 +207,10 @@ const LUA_REG_TYPE adc_map[] =
   { LSTRKEY( "setblocking" ), LFUNCVAL( adc_setblocking ) },
   { LSTRKEY( "setsmoothing" ), LFUNCVAL( adc_setsmoothing ) },
   { LSTRKEY( "getsample" ), LFUNCVAL( adc_getsample ) },
+#if defined( BUF_ENABLE_ADC )
   { LSTRKEY( "getsamples" ), LFUNCVAL( adc_getsamples ) },
 //  { LSTRKEY( "putsamples" ), LFUNCVAL( adc_putsamples ) },
+#endif
   { LNILKEY, LNILVAL }
 };
 

src/platform/lm3s/platform.c

@@ -554,13 +554,17 @@ void ADCIntHandler( void )
   {
     s = d->ch_state[ d->seq_ctr ];
     d->sample_buf[ d->seq_ctr ] = ( u16 )tmpbuff[ d->seq_ctr ];
+    s->value_fresh = 1; // Mark sample as fresh
     
     // Fill in smoothing buffer until warmed up
     if ( s->logsmoothlen > 0 && s->smooth_ready == 0)
       adc_smooth_data( s->id );
 #if defined( BUF_ENABLE_ADC )
     else
+    {
       buf_write( BUF_ID_ADC, s->id, ( t_buf_data* )s->value_ptr );
+      s->value_fresh = 0;
+    }
 #endif
 
     // If we have the number of requested samples, stop sampling

src/platform/stm32/platform.c

@@ -648,13 +648,17 @@ void DMA1_Channel1_IRQHandler(void)
   while( d->seq_ctr < d->seq_len )
   {
     s = d->ch_state[ d->seq_ctr ];
+    s->value_fresh = 1;
     
     // Fill in smoothing buffer until warmed up
     if ( s->logsmoothlen > 0 && s->smooth_ready == 0)
       adc_smooth_data( s->id );
 #if defined( BUF_ENABLE_ADC )
     else
+    {
       buf_write( BUF_ID_ADC, s->id, ( t_buf_data* )s->value_ptr );
+      s->value_fresh = 0;
+    }
 #endif
 
     // If we have the number of requested samples, stop sampling