From: David Schleef <ds@schleef.org>
Date: Fri, 8 Jun 2001 22:36:34 +0000 (+0000)
Subject: More busy-talk about counters
X-Git-Tag: r0_7_60~178
X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=68f2a7ef66f5f29118972b12b39e74c9c54d1e91;p=comedi.git

More busy-talk about counters
---

diff --git a/Documentation/comedi/counter-spec b/Documentation/comedi/counter-spec
index 3daeaa0c..9eb92f8f 100644
--- a/Documentation/comedi/counter-spec
+++ b/Documentation/comedi/counter-spec
@@ -1,4 +1,81 @@
 
+A counter is an input device, "counting" the number of triggers
+that occur while the gate is enabled.  A timer is an output
+device.
+
+counter "command"
+
+{
+	unsigned int	mode;
+
+	unsigned int	src1_src;
+	unsigned int	src1_arg;
+
+	unsigned int	src2_src;
+	unsigned int	src2_arg;
+
+	unsigned int	gate_src;
+	unsigned int	gate_arg;
+}
+
+Counter examples:
+
+  (Unless otherwise specified, _src's are TRIG_NONE.)
+
+  Counting up at a rate of 1/ms:
+
+    mode = UP_COUNTER;
+    src1_src = TRIG_TIMER;
+    src1_arg = 1000000;
+
+  Counting down at a rate of 1/ms:
+
+    mode = DOWN_COUNTER;
+    arg1_src = TRIG_TIMER;
+    arg1_arg = 1000000;
+
+  Counting up at each rising transition of digital input 4:
+
+    mode = UP_COUNTER;
+    src1_src = TRIG_EXT;
+    src1_arg = 4 | TRIG_EXT_RISING;
+
+  Quadrature counting on di 0,1:
+  
+    mode = QUADRATURE;
+    src1_src = TRIG_EXT;
+    src1_arg = 0;
+    src2_src = TRIG_EXT;
+    src1_arg = 1;
+
+  Interval timing of digital input 4:
+
+    Counter setup:
+
+      mode = UP_COUNTER;
+      src1_src = TRIG_TIMER;
+      gate_src = TRIG_EXT;
+      gate_arg = 4 | LEVEL_1;
+      event_src = TRIG_EXT;
+      event_arg = 4 | FALLING_EDGE;
+
+      flags = COUNT_RESET; /* counter resets at every event */
+
+    Command setup:
+
+      start_src = TRIG_NOW;
+      scan_begin_src = TRIG_NOW;
+      convert_src = TRIG_FOLLOW;
+      scan_end_src = TRIG_COUNT;
+      scan_end_arg = 1;
+      stop_src = whatever;
+  
+
+Timer examples:
+
+
+
+
 Counters are based on a number of digital inputs, typically
 2 or 3, and the count is changed due to the transition of
 one line and the status of other lines.