Fix circular buffer to overflow properly (#1163)

* Bug fix, the instance comparision was wrong

* Update circular buffer to take into account the number of channels being sampled

* Update cb_init function, remove floating operations from the microblaze. Fix the computation of the log_capacity

* Fix variable name

* Add head overflow in the circular buffer structure to allow reseting it everytime it's initialized

* Remove overflow bit

* Enhance class to support a single channel

* Update changelog

* Modify MAX_SAMPLES to be multiple of 1, 2 and 3 channels

* Fix comments

* Include 'raw' APIs calling for backwards compatibility

boards/Pynq-Z1/base/notebooks/arduino/arduino_analog.ipynb

@@ -66,7 +66,7 @@
     {
      "data": {
       "text/plain": [
-       "[0.6403, 0.6848]"
+       "array([0.6403, 0.6848])"
       ]
      },
      "execution_count": 3,
@@ -106,7 +106,7 @@
     }
    ],
    "source": [
-    "analog1.read_raw()[0]"
+    "analog1.read('raw')[0]"
    ]
   },
   {
@@ -196,6 +196,8 @@
     "                  'bs', label=\"Y-axis of joystick\")\n",
     "plt.title('Arduino Analog Voltage Log')\n",
     "plt.axis([0, len(log1[0]), 0.0, 3.3])\n",
+    "plt.xlabel('Sample number')\n",
+    "plt.ylabel('Voltage')\n",
     "plt.legend(loc=4,bbox_to_anchor=(1, -0.3),\n",
     "           ncol=2, borderaxespad=0.,\n",
     "           handler_map={line1: HandlerLine2D(numpoints=1),\n",
@@ -294,6 +296,8 @@
     "                  'g^', label=\"potentiometer\")\n",
     "plt.title('Arduino Analog Voltage Log')\n",
     "plt.axis([0, len(log2[0]), 0.0, 3.3])\n",
+    "plt.xlabel('Sample number')\n",
+    "plt.ylabel('Voltage')\n",
     "plt.legend(loc=4,bbox_to_anchor=(1, -0.3),\n",
     "           ncol=2, borderaxespad=0.,\n",
     "           handler_map={line1: HandlerLine2D(numpoints=1),\n",

boards/sw_repo/pynqmb/src/circular_buffer.c

@@ -46,6 +46,8 @@
  * 1.00  yrq 01/09/18 release
  * 1.01  mrn 09/28/20 Bug fix, the head of the circular 
  *                    buffer did not overflow
+ * 1.02  mrn 10/11/20 Update initialize function. Bug fix: move the head 
+ *                    according to the number of channels.
  *
  * </pre>
  *
@@ -54,13 +56,14 @@
 
 /************************** Function Definitions ***************************/
 int cb_init(circular_buffer *cb, volatile u32* log_start_addr,
-            size_t capacity, size_t sz){
+            size_t capacity, size_t sz, size_t channels){
     cb->buffer = (volatile char*) log_start_addr;
     if(cb->buffer == NULL)
         return -1;
     cb->buffer_end = (char *)cb->buffer + capacity * sz;
     cb->capacity = capacity;
     cb->sz = sz;
+    cb->channels = channels;
     cb->head = cb->buffer;
     cb->tail = cb->buffer;
 
@@ -106,11 +109,11 @@ void cb_push_incr_ptrs(circular_buffer *cb){
         cb->tail = cb->buffer;
 
     if (cb->tail == cb->head) {
-        cb->head  = (char*)cb->head + cb->sz;
+        cb->head  = (char*)cb->head + cb->sz * cb->channels;
+        // Move the head pointer to buffer start
         if (cb->head >= cb->buffer_end)
             cb->head = cb->buffer;
     }
-
     // update mailbox head and tail
     MAILBOX_DATA(2) = (u32) cb->head;
     MAILBOX_DATA(3) = (u32) cb->tail;

boards/sw_repo/pynqmb/src/circular_buffer.h

@@ -44,6 +44,7 @@
  * Ver   Who  Date     Changes
  * ----- --- ------- -----------------------------------------------
  * 1.00  yrq 01/09/18 release
+ * 1.01  mrn 10/11/18 Include channels in the init function.
  *
  * </pre>
  *
@@ -72,7 +73,7 @@ typedef struct circular_buffer
   volatile void *buffer;     // data buffer
   void *buffer_end;          // end of data buffer
   size_t capacity;           // maximum number of items in the buffer
-  size_t count;              // number of items in the buffer
+  size_t channels;           // number of channels in the buffer
   size_t sz;                 // size of each item in the buffer
   volatile void *head;       // pointer to head
   volatile void *tail;       // pointer to tail
@@ -81,7 +82,7 @@ typedef struct circular_buffer
 circular_buffer circular_log;
 
 int cb_init(circular_buffer *cb, volatile u32* log_start_addr,
-            size_t capacity, size_t sz);
+            size_t capacity, size_t sz, size_t channels);
 void cb_push_back(circular_buffer *cb, const void *item);
 void cb_push_back_float(circular_buffer *cb, const float *item);
 void cb_push_incr_ptrs(circular_buffer *cb);

docs/source/overlay_design_methodology/pynq_microblaze_subsystem.rst

@@ -803,7 +803,8 @@ Remaining code:
 
          case READ_AND_LOG:
        // initialize logging variables, reset cmd
-       cb_init(&circular_log, LOG_BASE_ADDRESS, LOG_CAPACITY, LOG_ITEM_SIZE);
+       cb_init(&circular_log, 
+         LOG_BASE_ADDRESS, LOG_CAPACITY, LOG_ITEM_SIZE, 1);
        delay = MAILBOX_DATA(1);
        MAILBOX_CMD_ADDR = 0x0;