Diff: main.cpp

Revision:

0:f3705ec14cf0

Child:

1:b2b2924c3c48

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sun Aug 23 17:00:09 2015 +0000
@@ -0,0 +1,79 @@
+/* 
+Heart rate example for the SiLabs biometrics board using the Si1146
+
+Since their own example code is all hidden behind precompiled libraries, here an 
+example which is actually useful :D. Take into account this is an example, I just screwed
+around a bit and observed some output waveforms to make it work reasonable, there are
+for sure better ways to implement this.
+
+User manual:
+If the Gecko symbol turns on on the LCD it is connected to the sensor
+Place your finger on the sensor. In the biometrics board manual it is explained how,
+but you can also try until it works properly. You don't want to use the extreme tip of your
+finger, but a bit further back.
+The battery indicator will flash briefly when a beat is detected. 
+
+Every beat it re-calculates your heartbeat using the time of the previous beat, since no
+filtering happens here, it can jump around a bit, but this should be limitted.
+
+And just to be sure since we can never overestimate human stupidity: This is not a medical tool...
+
+
+Todo: 
+1. Get rid of my hardcoded value used as threshold
+2. Measure PO2
+*/
+
+
+#include "mbed.h"
+#include "Si114x.h"
+#include "EFM32_SegmentLCD.h"
+
+
+DigitalOut myled(LED1);
+silabs::EFM32_SegmentLCD segmentDisplay;
+        
+
+int main() {
+    segmentDisplay.AllOff();
+    Si114x sensor(PD6, PD7);
+    while(sensor.verifyConnection() != 1);
+    segmentDisplay.Symbol(LCD_SYMBOL_GECKO, 1);
+    
+    int curval;
+    int prevval = 0;
+    int mvingavg[3] = {0};
+    int sum;
+    int prevtime = 0;
+    int timesincelast;
+    
+    Timer timey;    
+    timey.start();
+    while(1) {
+        curval=sensor.getProximity(2);      //We use visible light, seems to work alot better than IR
+        
+        //Three times moving average of the diff of the output
+        mvingavg[2] = mvingavg[1];
+        mvingavg[1] = mvingavg[0];
+        mvingavg[0] = curval - prevval;
+        sum = mvingavg[2] + mvingavg[1] + mvingavg[0];
+        
+        //Magic number for minimum threshold before it sees something as a heartbeat, adjust if my fingers are special :)
+        if (sum < -50) {
+            segmentDisplay.Battery(4);
+            timesincelast = timey.read_ms() - prevtime;
+            if (timesincelast > 250) {
+                uint32_t hearthrate = 60000 / timesincelast;
+                segmentDisplay.Number(hearthrate);
+                prevtime = timey.read_ms();
+            }
+        }
+        else {
+            segmentDisplay.Battery(0);
+        }
+        
+        prevval = curval;
+    
+}
+    
+}
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