From dd9050e0aabb47622167174697861ab9cce4cd57 Mon Sep 17 00:00:00 2001
From: Noel Eck <noel.eck@intel.com>
Date: Wed, 28 Sep 2016 11:47:16 -0700
Subject: [PATCH] dfrph: Updated to use mraa read_float

Use mraa's normalized adc read.  Updated names of struct
members accordingly.

Signed-off-by: Noel Eck <noel.eck@intel.com>
---
 src/dfrph/dfrph.c | 29 ++++++++++++-----------------
 src/dfrph/dfrph.h |  4 ++--
 2 files changed, 14 insertions(+), 19 deletions(-)

diff --git a/src/dfrph/dfrph.c b/src/dfrph/dfrph.c
index 21735bcd..1cde8ce1 100644
--- a/src/dfrph/dfrph.c
+++ b/src/dfrph/dfrph.c
@@ -39,8 +39,8 @@ dfrph_context dfrph_init(int16_t pin)
 
     /* Set the ref, offset, and scale */
     dev->m_aref = 5.0;
-    dev->m_count_offset = 0.0;
-    dev->m_count_scale = 1.0;
+    dev->m_offset = 0.0;
+    dev->m_scale = 1.0;
 
     if(dev->aio == NULL) {
         free(dev);
@@ -69,13 +69,13 @@ float dfrph_get_aref(const dfrph_context dev)
 
 upm_result_t dfrph_set_offset(const dfrph_context dev, float offset)
 {
-    dev->m_count_offset = offset;
+    dev->m_offset = offset;
     return UPM_SUCCESS;
 }
 
 upm_result_t dfrph_set_scale(const dfrph_context dev, float scale)
 {
-    dev->m_count_scale = scale;
+    dev->m_scale = scale;
     return UPM_SUCCESS;
 }
 
@@ -92,23 +92,18 @@ upm_result_t dfrph_get_raw_volts(const dfrph_context dev, float *volts)
 
 upm_result_t dfrph_get_ph(const dfrph_context dev, float *value)
 {
-    /* Read counts */
-    int counts = mraa_aio_read(dev->aio);
+    /* Read normalized */
+    *value = mraa_aio_read_float(dev->aio);
+    if (*value < 0.0) return UPM_ERROR_OPERATION_FAILED;
 
-    /* Get max adc value range 1023, 2047, 4095, etc... */
-    float max_adc = (1 << mraa_aio_get_bit(dev->aio)) - 1;
-
-    /* Apply raw scale */
-    *value = counts * dev->m_count_scale;
-
-    /* Apply raw offset */
-    *value += dev->m_count_offset * dev->m_count_scale;
-
-    /* Normalize the value */
-    *value /= max_adc;
+    /* Apply scale */
+    *value *= dev->m_scale;
 
     /* Vmax for sensor is 0.8 * Vref, so scale by 1/0.8 = 1.25 */
     *value *= 1.25 * 14; /* Convert to pH */
 
+    /* Apply offset in pH */
+    *value += dev->m_offset;
+
     return UPM_SUCCESS;
 }
diff --git a/src/dfrph/dfrph.h b/src/dfrph/dfrph.h
index 5829a8d8..30aea712 100644
--- a/src/dfrph/dfrph.h
+++ b/src/dfrph/dfrph.h
@@ -48,9 +48,9 @@ typedef struct _dfrph_context {
     /* ADC reference */
     float m_aref;
     /* Raw count offset */
-    float m_count_offset;
+    float m_offset;
     /* Raw count scale */
-    float m_count_scale;
+    float m_scale;
 } *dfrph_context;
 
 /**