-The implementation of the 12-bit ADC stack on the MSP430 is in compliance with
-TEP 101 (tinyos-2.x/doc/txt/tep101.txt) and provides virtualized access to the
-ADC12 by seven different components: AdcReadClientC, AdcReadNowClientC,
+The implementation of the 12-bit ADC stack on the MSP430 is in compliance
+with TEP 101 (tinyos-2.x/doc/txt/tep101.txt) and provides virtualized access
+to the ADC12 by seven different components: AdcReadClientC, AdcReadNowClientC,
AdcReadStreamClientC, Msp430Adc12ClientC, Msp430Adc12ClientAutoDMAC,
Msp430Adc12ClientAutoRVGC and Msp430Adc12ClientAutoDMA_RVGC. A client
component may wire to any of these components and it SHOULD NOT wire to any
explains the difference between the seven components.
+1. HIL
+====================================================================
+
+
A platform-independent application (an application like 'Oscilloscope' that is
supposed to run on, for example, the 'telosb' and 'micaz' platform at the same
time) cannot wire to an MSP430-specific interface like Msp430Adc12SingleChannel
rather about portability it should wire to any of these components.
+2. HAL
+====================================================================
+
An application that is written for an MSP430-based platform like 'eyesIFX' or
-'telosb' can access the ADC12 in a more efficient way to, for example, do
-high-frequency sampling through the Msp430Adc12SingleChannel interface. On the
-MSP430 two additional hardware modules may become relevant when the ADC12 is
-used: the internal reference voltage generator and the DMA controller. The
-voltage generator outputs stabilized voltage of 1.5 V or 2.5 V, which may be
-used as reference voltage in the conversion process. Whether the internal
+'telosb' can access the ADC12 in a more efficient way via two interfaces: (1)
+the Msp430Adc12SingleChannel allows to perform one or more ADC conversions on a
+single channel with a specified sampling frequency and (2) the
+Msp430Adc12MultiChannel allows to sample a group of up to 16 different ADC
+channels "at once" (with minimum latency) and in addition define a sampling
+frequency for the whole group (useful for multi-channel accelerometers, etc.).
+On the MSP430 two additional hardware modules may play a role when the ADC12 is
+used: the internal reference voltage generator and the DMA controller.
+
+The voltage generator outputs stabilized voltage of 1.5 V or 2.5 V, which may
+be used as reference voltage in the conversion process. Whether the internal
reference voltage generator should be enabled during the conversion is
platform-specific (e.g. the light sensor on the 'eyesIFX' requires a stable
reference voltage). When an application requires a stable reference voltage
during the sampling process it should wire to the Msp430Adc12ClientAutoRVGC
component. This assures that when the app is signalled the Resource.granted()
event the reference voltage generator outputs a stable voltage (the level is
-defined in the configuration data supplied by the application). The DMA
-controller can be used to efficiently copy conversion data from ADC data
-registers to the application buffer. DMA is only present on MSP430x15x and
-MSP430x16x devices. When an application wants to use the DMA it can wire to
-the Msp430Adc12ClientAutoDMAC component and then conversion results are
-transferred using DMA. Both, enabling the reference generator and using the
-DMA, therefore happens transparent to the app. There are four possible
-combinations reflected by the following components that an MSP430-based
-application may wire to:
+defined in the configuration data supplied by the application). There are two
+more things to note: first, the generator is not switched off immediately, when
+the client calls Resource.release(), but only after some pre-defined interval
+(see Msp430RefVoltGenerator.h). This can avoid a power-up delay when multiple
+clients are present. Second, one must not forget to wire the AdcConfigure
+interface to the Msp430Adc12ClientAutoRVGC or Msp430Adc12ClientAutoDMA_RVGC
+component in addition to configuring the ADC through the
+Msp430Adc12SingleChannel interface (a nesC warning will be signalled).
+
+The DMA controller can be used to copy conversion data from the ADC registers
+to the application buffer. DMA is only present on MSP430x15x and MSP430x16x
+devices. When an application wants to use the DMA it can wire to the
+Msp430Adc12ClientAutoDMAC component and then conversion results are transferred
+using DMA. Both, enabling the reference generator and using the DMA, therefore
+happens transparent to the app. There are four possible combinations reflected
+by the following components that an MSP430-based application may wire to:
* Msp430Adc12ClientC: no DMA, no automatic reference voltage
* Msp430Adc12ClientAutoRVGC: automatic reference voltage, but no DMA
* Msp430Adc12ClientAutoDMAC: DMA, but no automatic reference voltage
* Msp430Adc12ClientAutoDMA_RVGC: DMA and automatic reference voltage
+Currently Msp430Adc12MultiChannel is only provided by the first two components.
+
+I/O PINs
+--------------------------------------------------------------------
+
During a conversion the respective ADC port pin (ports 6.0 - 6.7) must be
configured such that the peripheral module function is selected and the port
pin is switched to input direction. By default, for every client this is done
conversion starts the respective pin is switched to peripheral module function
and input direction and immediately after the conversion has finished it is
switched to I/O function mode. To disable this feature please comment out the
-"P6PIN_AUTO_CONFIGURE" macro in Msp430Adc12.h.
+"ADC12_P6PIN_AUTO_CONFIGURE" macro in Msp430Adc12.h.
+
+
+Configuration for single channel conversions
+--------------------------------------------------------------------
+
+The msp430adc12_channel_config_t struct holds all information needed to
+configure the ADC12 for single channel conversions. The flags come from the
+following MSP430 registers: ADC12CTL0, ADC12CTL1, ADC12MCTLx and TACTL and are
+named according to the "MSP430x1xx Family User's Guide". Their meaning is as
+follows:
+
+ .inch: ADC12 input channel (ADC12MCTLx register). An (external) input
+ channel maps to one of msp430's A0-A7 pins (see device specific data sheet).
+
+ .sref: reference voltage (ADC12MCTLx register). If REFERENCE_VREFplus_AVss
+ or REFERENCE_VREFplus_VREFnegterm is chosen AND the client wires to the
+ Msp430Adc12ClientAutoRVGC or Msp430Adc12ClientAutoDMA_RVGC component then
+ the reference voltage generator has automatically been enabled to the
+ voltage level defined by the "ref2_5v" flag (see below) when the
+ Resource.granted() event is signalled to the client. Otherwise this flag is
+ ignored.
+
+ .ref2_5v: Reference generator voltage level (ADC12CTL0 register). See
+ "sref".
+
+ .adc12ssel: ADC12 clock source select for the sample-hold-time (ADC12CTL1
+ register). In combination the "adc12ssel", "adc12div" and "sht" define the
+ sample-hold-time: "adc12ssel" defines the clock source, "adc12div" defines
+ the ADC12 clock divider and "sht" define the time expressed in jiffies.
+ (the sample-hold-time depends on the resistence of the attached sensor, and
+ is calculated using to the formula in section 17.2.4 of the user guide)
+
+ .adc12div: ADC12 clock divider (ADC12CTL1 register). See "adc12ssel".
+
+ .sht: Sample-and-hold time (ADC12CTL1 register). See "adc12ssel".
+
+ .sampcon_ssel: Clock source for the sampling period (TASSEL for TimerA).
+ When an ADC client specifies a non-zero "jiffies" parameter (using the
+ Msp430Adc12SingleChannel.configureX commands), the ADC
+ implementation will automatically configure TimerA to be sourced from
+ "sampcon_ssel" with an input divider of "sampcon_id". During the sampling
+ process TimerA will be used to trigger a single
+ (Msp430Adc12SingleChannel interface) or a sequence of (Msp430Adc12MultiChannel
+ interface) conversions every "jiffies" clock ticks.
+
+ .sampcon_id: Input divider for "sampcon_ssel" (IDx in TACTL register,
+ TimerA). See "sampcon_ssel".
+
+
+Example: Assuming that SMCLK runs at 1 MHz the following code snippet
+performs 2000 ADC conversions on channel A2 with a sampling period of 4000 Hz.
+The sampling period is defined by the combination of SAMPCON_SOURCE_SMCLK,
+SAMPCON_CLOCK_DIV_1 and a "jiffies" parameter of (1000000 / 4000) = 250.
+
+
+ #define NUM_SAMPLES 2000
+ uint16_t buffer[NUM_SAMPLES];
+
+ const msp430adc12_channel_config_t config = {
+ INPUT_CHANNEL_A2, REFERENCE_VREFplus_AVss, REFVOLT_LEVEL_NONE,
+ SHT_SOURCE_SMCLK, SHT_CLOCK_DIV_1, SAMPLE_HOLD_64_CYCLES,
+ SAMPCON_SOURCE_SMCLK, SAMPCON_CLOCK_DIV_1
+ };
+
+ event void Boot.booted()
+ {
+ call Resource.request();
+ }
+
+ event void Resource.granted()
+ {
+ error_t result;
+ result = call SingleChannel.configureMultiple(&config, buffer, BUFFER_SIZE, 250);
+ if (result == SUCCESS)
+ call SingleChannel.getData();
+ }
+
+ async event uint16_t* SingleChannel.multipleDataReady(uint16_t *buf, uint16_t length)
+ {
+ // buffer contains conversion results
+ }
+
+
+3. Implementation
+====================================================================
+
+The ADC12 stack is located at tinyos-2.x/tos/chips/msp430/adc12. Sensor
+wrappers for the msp430 internal sensors are in
+tinyos-2.x/tos/chips/msp430/sensors, an HAL test app can be found in
+tinyos-2.x/apps/tests/msp430/Adc12.
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projects / tinyos-2.x.git / blobdiff