MAJOR refactoring of Sensors code

[matches/MCTX3420.git] / server / sensors / strain.c

diff --git a/server/sensors/strain.c b/server/sensors/strain.c
new file mode 100644 (file)
index 0000000..3ee1624
--- /dev/null
+++ b/server/sensors/strain.c
@@ -0,0 +1,102 @@
+#include "strain.h"
+
+#include "../log.h"
+#include "../bbb_pin.h"
+
+#include <pthread.h>
+
+#define STRAIN_ADC ADC0
+
+/**
+ * Convert Strain gauge id number to a GPIO pin on the Mux
+ * @param id - The strain gauge id
+ * @returns - GPIO pin number
+ */
+static int Strain_To_GPIO(StrainID id)
+{
+       // Could use a lookup table; that would assume strict ordering of the enum in strain.h
+       //static int lookup[] = {GPIO0_30, GPIO1_28,GPIO0_31,GPIO1_16};
+       //if (id < STRAIN0 || id > STRAIN3)
+       //      Fatal("unknown strain id %d", id);
+       //return lookup[id];
+
+       switch (id)
+       {
+               case STRAIN0:
+                       return GPIO0_30;
+               case STRAIN1:
+                       return GPIO1_28;
+               case STRAIN2:
+                       return GPIO0_31;
+               case STRAIN3:
+                       return GPIO1_16;
+               default:
+                       Fatal("Unknown StrainID %d", id);
+                       return -1; // Should never happen
+       }
+}
+
+/**
+ * Convert ADC Strain reading to a physically meaningful value
+ * @param reading - The ADC reading
+ * @returns Something more useful
+ */
+static double Strain_Calibrated(int reading)
+{
+       return (double)(reading);
+}
+
+/**
+ * Initialise a Strain gauge
+ * @param id - The strain gauge to initialise
+ * @param name - Name of the strain gauge; ignored
+ * @returns true if initialisation was successful
+ */
+bool Strain_Init(const char * name, int id)
+{
+       int gpio_num = Strain_To_GPIO(id);
+       GPIO_Export(gpio_num);
+       if (!GPIO_Set(gpio_num, false))
+               Fatal("Couldn't set GPIO%d for strain sensor %d to LOW", gpio_num, id);
+
+       static bool init_adc = false;
+       if (!init_adc)
+       {
+               init_adc = true;
+               ADC_Export(STRAIN_ADC);
+       }
+       return true;
+}
+
+/**
+ * Read from a Strain gauge
+ * @param id - The strain gauge to read
+ * @param val - Will store the read value if successful
+ * @returns true on successful read
+ */
+bool Strain_Read(int id, double * value)
+{
+       static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; // CRITICAL SECTION - Only one Strain gauge can be read at a time
+       pthread_mutex_lock(&mutex);
+
+       int gpio_num = Strain_To_GPIO(id);
+       
+       // Set the multiplexer
+       if (!GPIO_Set(gpio_num, true))
+               Fatal("Couldn't set GPIO%d for strain sensor %d to HIGH (before reading)", gpio_num,id);
+
+       // Read the ADC
+       int tmp = 0;
+       bool result = ADC_Read(STRAIN_ADC, &tmp); // If this fails, it's not fatal
+       
+       //TODO: Callibrate?
+       *value = Strain_Calibrated(tmp);
+
+       // Unset the multiplexer
+       if (!GPIO_Set(gpio_num, false))
+               Fatal("Couldn't set GPIO%d for strain sensor %d to LOW (after reading)", gpio_num, id);
+
+       pthread_mutex_unlock(&mutex);
+
+       return result;
+}