Milosch Meriac
Discrete RGB colour sensor using a colour LED flashing at high speed and a monochrome LDR (light dependent resistor) for detecting the colour via ADC conversion. The library implements interrupt driven ADC conversion at high speed (370 RGB readings per second, 128 times oversampling per channelfor noise reduction). The detection can optionally run in background.
Dependents: rgb_sensor_buffer discrete_rgb_color_sensor_example
Diff: rgb_sensor.cpp
- Revision:
- 5:1fed2b68e661
- Parent:
- 4:0ffadc2caaf6
- Child:
- 6:fc64a14a2f4a
--- a/rgb_sensor.cpp Fri Jun 27 12:14:36 2014 +0000
+++ b/rgb_sensor.cpp Sat Jun 28 06:59:51 2014 +0000
@@ -106,6 +106,32 @@
m_global->adc_irq();
}
+int RGB_Sensor::filter(int sample)
+{
+ int a,b,x,y,z;
+
+ /* get the two previous samples */
+ a = m_adc_filter[m_rgb_channel][0];
+ b = m_adc_filter[m_rgb_channel][1];
+
+ /* calculate node distances in triplet */
+ x = abs(a-sample);
+ y = abs(b-sample);
+ z = abs(a-b);
+
+ /* remember current sample */
+ m_adc_filter[m_rgb_channel][m_adc_filter_pos] = sample;
+ m_adc_filter_pos ^= 1;
+
+ /* choose edge with shortest distance and
+ * return average of the two edge nodes */
+ if((x<=y) && (x<=z))
+ return (a+sample)/2;
+ if((y<=x) && (y<=z))
+ return (b+sample)/2;
+ return (a+b)/2;
+}
+
void RGB_Sensor::adc_irq(void)
{
uint32_t sample, status;
@@ -118,7 +144,8 @@
if(!m_done)
{
- m_adc_aggregation[m_rgb_channel] += sample;
+ /* filter value to remove ADC noise/conversion errors */
+ m_adc_aggregation[m_rgb_channel] += filter(sample);
m_adc_count++;
if(m_adc_count>=RGB_OVERSAMPLING)
@@ -176,6 +203,9 @@
m_done = false;
m_adc_count = m_rgb_channel = 0;
memset((void*)&m_adc_aggregation, 0, sizeof(m_adc_aggregation));
+ m_adc_filter_pos = 0;
+ memset(&m_adc_filter, 0, sizeof(m_adc_filter));
+
/* start ADC burst mode */
LPC_ADC->ADCR |= (1UL<<16);