ADC

Low-level ADC peripheral driver interface. More...

Detailed Description

Low-level ADC peripheral driver interface.

This is a very simple ADC interface to allow platform independent access to a MCU's ADC unit(s). This interface is intentionally designed as simple as possible, to allow for very easy implementation and maximal portability.

As of now, the interface does not allow for any advanced ADC concepts (e.g. continuous mode, scan sequences, injections). It is to be determined, if these features will ever be integrated in this interface, or if it does make more sense to create a second, advanced ADC interface for this.

The ADC driver interface is built around the concept of ADC lines. An ADC line in this context is a tuple consisting out of a hardware ADC device (an ADC functional unit on the MCU) and an ADC channel connected to pin.

If a MCU has more than one hardware ADC unit, the ADC lines can be mapped in a way, that it is possible to sample multiple lines in parallel, given that the ADC implementation allows for interruption of the program flow while waiting for the result of a conversion (e.g. through putting the calling thread to sleep while waiting for the conversion results).

(Low-) Power Implications

The ADC peripheral(s) should only be powered on while adc_sample() is active. For implementing adc_sample() this means, that the peripheral should be powered on (i.e. through peripheral clock gating) at the beginning of the function and it should be powered back off at the end of the function.

If the adc_sample() function is implemented in a way, that it will put the active thread to sleep for a certain amount of time, the implementation might need to block certain power states.

Todo:

Extend interface for continuous mode?

Files
file	adc.h
	Low-level ADC peripheral driver interface definitions.

Macros
#define	ADC_UNDEF   (UINT_MAX)
	Default ADC undefined value.
#define	ADC_LINE(x)   (x)
	Default ADC line access macro.

Typedefs
typedef unsigned int	adc_t
	Define default ADC type identifier.

Enumerations
enum	adc_res_t {   ADC_RES_6BIT = 0, ADC_RES_8BIT, ADC_RES_10BIT, ADC_RES_12BIT,   ADC_RES_14BIT, ADC_RES_16BIT }
	Possible ADC resolution settings. More...

Functions
int	adc_init (adc_t line)
	Initialize the given ADC line. More...
int32_t	adc_sample (adc_t line, adc_res_t res)
	Sample a value from the given ADC line. More...

Enumeration Type Documentation

adc_res_t

enum adc_res_t

Possible ADC resolution settings.

Enumerator
ADC_RES_6BIT	ADC resolution: 6 bit.
ADC_RES_8BIT	ADC resolution: 8 bit.
ADC_RES_10BIT	ADC resolution: 10 bit.
ADC_RES_12BIT	ADC resolution: 12 bit.
ADC_RES_14BIT	ADC resolution: 14 bit.
ADC_RES_16BIT	ADC resolution: 16 bit.

Definition at line 93 of file adc.h.

Function Documentation

adc_init()

int adc_init

(

adc_t

line

)

Initialize the given ADC line.

The ADC line is initialized in synchronous, blocking mode.

Parameters

[in]

line

line to initialize

Returns

0 on success

-1 on invalid ADC line

adc_sample()

int32_t adc_sample	(	adc_t	line,
		adc_res_t	res
	)

Sample a value from the given ADC line.

This function blocks until the conversion has finished. Please note, that if more than one line share the same ADC device, and if these lines are sampled at the same time (e.g. from different threads), the one called secondly waits for the first to finish before its conversion starts.

Parameters

[in]	line	line to sample
[in]	res	resolution to use for conversion

Returns

the sampled value on success

-1 if resolution is not applicable