Added macros that can be used to reduce codesize (Msp430Adc12.h).

[tinyos-2.x.git] / tos / chips / msp430 / adc12 / README.txt

diff --git a/tos/chips/msp430/adc12/README.txt b/tos/chips/msp430/adc12/README.txt
index 7acc1c116bb6a49b618db08d61401072c26aa6b1..6a6ca684983c1b08689fc42c5380063655601d0f 100644 (file)
--- a/tos/chips/msp430/adc12/README.txt
+++ b/tos/chips/msp430/adc12/README.txt
@@ -32,35 +32,48 @@ rather about portability it should wire to any of these components.
 ====================================================================
 
 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.
 
-PINs
+I/O PINs
 --------------------------------------------------------------------
 
 During a conversion the respective ADC port pin (ports 6.0 - 6.7) must be
@@ -70,7 +83,7 @@ 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
@@ -153,6 +166,15 @@ SAMPCON_CLOCK_DIV_1 and a "jiffies" parameter of (1000000 / 4000) = 250.
     // 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.
+
 -----
 
 $Date$