px4io: return raw ADC value for current

we don't know how to scale it as we have no info on what sensor is
attached. As we are returning a uint16_t it is better to let the FMU
sort it out or we'll just lose precision.

src/modules/px4iofirmware/protocol.h

@@ -115,7 +115,7 @@
 #define PX4IO_P_STATUS_ALARMS_PWM_ERROR		(1 << 6) /* PWM configuration or output was bad */
 
 #define PX4IO_P_STATUS_VBATT			4	/* battery voltage in mV */
-#define PX4IO_P_STATUS_IBATT			5	/* battery current in cA */
+#define PX4IO_P_STATUS_IBATT			5	/* battery current (raw ADC) */
 
 /* array of post-mix actuator outputs, -10000..10000 */
 #define PX4IO_PAGE_ACTUATORS		2		/* 0..CONFIG_ACTUATOR_COUNT-1 */
@@ -155,8 +155,6 @@
 #define PX4IO_P_SETUP_PWM_ALTRATE		4	/* 'high' PWM frame output rate in Hz */
 #define PX4IO_P_SETUP_RELAYS			5	/* bitmask of relay/switch outputs, 0 = off, 1 = on */
 #define PX4IO_P_SETUP_VBATT_SCALE		6	/* battery voltage correction factor (float) */
-#define PX4IO_P_SETUP_IBATT_SCALE		7	/* battery current scaling factor (float) */
-#define PX4IO_P_SETUP_IBATT_BIAS		8	/* battery current bias value */
 #define PX4IO_P_SETUP_SET_DEBUG			9	/* debug level for IO board */
 
 /* autopilot control values, -10000..10000 */

src/modules/px4iofirmware/registers.c

@@ -138,8 +138,6 @@ volatile uint16_t	r_page_setup[] =
 	[PX4IO_P_SETUP_PWM_ALTRATE]		= 200,
 	[PX4IO_P_SETUP_RELAYS]			= 0,
 	[PX4IO_P_SETUP_VBATT_SCALE]		= 10000,
-	[PX4IO_P_SETUP_IBATT_SCALE]		= 0,
-	[PX4IO_P_SETUP_IBATT_BIAS]		= 0,
 	[PX4IO_P_SETUP_SET_DEBUG]		= 0,
 };
 
@@ -516,12 +514,14 @@ registers_get(uint8_t page, uint8_t offset, uint16_t **values, unsigned *num_val
 
 		/* PX4IO_P_STATUS_IBATT */
 		{
-			unsigned counts = adc_measure(ADC_VBATT);
-			unsigned scaled = (counts * r_page_setup[PX4IO_P_SETUP_IBATT_SCALE]) / 10000;
-			int corrected = scaled + REG_TO_SIGNED(r_page_setup[PX4IO_P_SETUP_IBATT_BIAS]);
-			if (corrected < 0)
-				corrected = 0;
-			r_page_status[PX4IO_P_STATUS_IBATT] = corrected;
+			/*
+			  note that we have no idea what sort of
+			  current sensor is attached, so we just
+			  return the raw 12 bit ADC value and let the
+			  FMU sort it out, with user selectable
+			  configuration for their sensor
+			 */
+			r_page_status[PX4IO_P_STATUS_IBATT] = adc_measure(ADC_IN5);
 		}
 
 		SELECT_PAGE(r_page_status);