messing with the adc

firmware/mcp_adc.c

@@ -20,49 +20,65 @@
  *
  */
 
+
 #define ADC_NEW_SAMPLE 0x80
+#define ADC_READ_DATA 0x40
+
 #define ADC_BITS_MASK 0x0c
 
 #define ADC_ADDR 0xD0 /* or 0x68 */
 
 uint8_t r[4];
+uint8_t curmode;
 
 void mcpadc_init(uint8_t mode)
 {
 	i2c_write(ADC_ADDR, 1, &mode);
+	curmode = mode;
 }
 
-uint8_t mcpadc_has_new_data()
+uint8_t mcpadc_has_new_data(void)
 {
-	i2c_read(ADC_ADDR, 4, r);/* 4 bytes are only needed in 18 bit mode */
-	return(r[3] & ADC_NEW_SAMPLE);
+	/* this assumes that the first RDY bit read after the sample data indicates the old/new state of the sample we just read */
+	if(curmode & ADC_BITS_MASK == ADC_BITS_18)
+	{
+		i2c_read(ADC_ADDR, 4, r);
+		curmode = r[4];
+	}
+	else
+	{
+		i2c_read(ADC_ADDR, 3, r);
+		curmode = r[3];
+	}
+	if(~curmode & ADC_NEW_SAMPLE) {curmode &= ADC_READ_DATA;}
+	return ~curmode & ADC_READ_DATA;
 }
 
 #if ADC_ENABLE_18_BIT_MODE
-int32_t mcpadc_get_data()
+int32_t mcpadc_get_data(void)
 {
 	int32_t value = 0;
-	i2c_read(ADC_ADDR, 4, r);/* reading 4 bytes guarantees us one config byte */
 	if(r[0] & 0x80) {value = 0xffff;}
-	value = (value << 16) | (r[0] << 8) | r[1];/*endianess ???*/
+	value = (value << 16) | (r[0] << 8) | r[1];
 	if((uint8_t) r[3] & ADC_BITS_MASK == ADC_BITS_18)
 	{
 		value = (value << 8) | r[2];
 	}
+	curmode |= (ADC_NEW_SAMPLE & ADC_READ_DATA);
 	return value;
 }
 #else
-int16_t mcpadc_get_data()
+int16_t mcpadc_get_data(void)
 {
-	i2c_read(ADC_ADDR, 2, r);/* this will NOT work in 18 bit mode */
-	int16_t value = (r[0] << 8) | r[1];/*endianess ???*/
+	int16_t value = (r[0] << 8) | r[1];
+	curmode |= (ADC_NEW_SAMPLE & ADC_READ_DATA);
 	return value;
 }
 #endif
 
-void mcpadc_start_conv()
+void mcpadc_start_conv(void)
 {
-	i2c_read(ADC_ADDR, 4, r);
-	r[3] |= ADC_NEW_SAMPLE;
+	r[3] = curmode | ADC_NEW_SAMPLE;
 	i2c_write(ADC_ADDR, 1, &(r[3]));
+	curmode |= (ADC_NEW_SAMPLE & ADC_READ_DATA);/* you asked for a new sample - no you won't get the old one */
 }

firmware/mcp_adc.h

@@ -1,15 +1,6 @@
 #ifndef MCPADC_H
 #define MCPADC_H
 
-/*
-
-used i2c functions:
-
-i2c_read(uint8_t address, uint length, uint8_t *buf);
-i2c_write(uint8_t address, uint length, uint8_t *buf);
-
-*/
-
 #define ADC_ENABLE_18_BIT_MODE 0
 
 #define ADC_GAIN_1 0x00
@@ -30,25 +21,25 @@ i2c_write(uint8_t address, uint length, uint8_t *buf);
 /* sets the mcp adc to the specified mode
  * valid modes are obtained by oring one of each group (ADC_GAIN_*, ADC_BITS_* and ADC_CONV_*) together
  */
-void mcpadc_init(uint8_t const mode);
+void mcpadc_init(uint8_t mode);
 
 /* tests if the adc has a new sample
  * returns nonzero if new data is aviable, 0 otherwise
  */
-uint8_t mcpadc_has_new_data();
+uint8_t mcpadc_has_new_data(void);
 
 /* returns the most recent sample result of the adc
  * !! return type depends on defines
  */
 #if ADC_ENABLE_18_BIT_MODE
-int32_t mcpadc_get_data();
+int32_t mcpadc_get_data(void);
 #else
-int16_t mcpadc_get_data();
+int16_t mcpadc_get_data(void);
 #endif
 
 /* instructs the adc to take a new sample now
  * has no effect if the current mode includes ADC_CONV_CONT
  */
-void mcpadc_start_conv();
+void mcpadc_start_conv(void);
 
 #endif