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dfrph: Updated to use mraa read_float

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

Signed-off-by: Noel Eck <noel.eck@intel.com>
This commit is contained in:
Noel Eck 2016-09-28 11:47:16 -07:00
parent eb7a3ceac7
commit dd9050e0aa
2 changed files with 14 additions and 19 deletions
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29
src/dfrph/dfrph.c
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@ -39,8 +39,8 @@ dfrph_context dfrph_init(int16_t pin)
/* Set the ref, offset, and scale */ /* Set the ref, offset, and scale */
dev->m_aref = 5.0; dev->m_aref = 5.0;
dev->m_count_offset = 0.0; dev->m_offset = 0.0;
dev->m_count_scale = 1.0; dev->m_scale = 1.0;
if(dev->aio == NULL) { if(dev->aio == NULL) {
free(dev); 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) upm_result_t dfrph_set_offset(const dfrph_context dev, float offset)
{ {
dev->m_count_offset = offset; dev->m_offset = offset;
return UPM_SUCCESS; return UPM_SUCCESS;
} }
upm_result_t dfrph_set_scale(const dfrph_context dev, float scale) upm_result_t dfrph_set_scale(const dfrph_context dev, float scale)
{ {
dev->m_count_scale = scale; dev->m_scale = scale;
return UPM_SUCCESS; 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) upm_result_t dfrph_get_ph(const dfrph_context dev, float *value)
{ {
/* Read counts */ /* Read normalized */
int counts = mraa_aio_read(dev->aio); *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... */ /* Apply scale */
float max_adc = (1 << mraa_aio_get_bit(dev->aio)) - 1; *value *= dev->m_scale;
/* 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;
/* Vmax for sensor is 0.8 * Vref, so scale by 1/0.8 = 1.25 */ /* Vmax for sensor is 0.8 * Vref, so scale by 1/0.8 = 1.25 */
*value *= 1.25 * 14; /* Convert to pH */ *value *= 1.25 * 14; /* Convert to pH */
/* Apply offset in pH */
*value += dev->m_offset;
return UPM_SUCCESS; return UPM_SUCCESS;
} }

4
src/dfrph/dfrph.h
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@ -48,9 +48,9 @@ typedef struct _dfrph_context {
/* ADC reference */ /* ADC reference */
float m_aref; float m_aref;
/* Raw count offset */ /* Raw count offset */
float m_count_offset; float m_offset;
/* Raw count scale */ /* Raw count scale */
float m_count_scale; float m_scale;
} *dfrph_context; } *dfrph_context;
/** /**