spi: Add some documentation, move OUTPUT_PROTO docs.

Add a short help text for the PD and move the OUTPUT_PROTO docs to pd.py
since they're not meant for the user too see.

2 files changed, 26 insertions, 20 deletions

diff --git a/decoders/spi/__init__.py b/decoders/spi/__init__.py
index 7527913..582891a 100644
--- a/decoders/spi/__init__.py
+++ b/decoders/spi/__init__.py
@@ -21,27 +21,13 @@
 '''
 Serial Peripheral Interface protocol decoder.
 
-Details:
-TODO
-
-Protocol output format:
-
-SPI packet:
-[<cmd>, <data1>, <data2>]
-
-Commands:
- - 'DATA': <data1> contains the MISO data, <data2> contains the MOSI data.
-   The data is _usually_ 8 bits (but can also be fewer or more bits).
-   Both data items are Python numbers, not strings.
- - 'CS CHANGE': <data1> is the old CS# pin value, <data2> is the new value.
-   Both data items are Python numbers (0/1), not strings.
-
-Examples:
- ['CS-CHANGE', 1, 0]
- ['DATA', 0xff, 0x3a]
- ['DATA', 0x65, 0x00]
- ['CS-CHANGE', 0, 1]
+This protocol decoder supports synchronous SPI(-like) protocols with a
+clock line, a MISO and MOSI line for data transfer in two directions,
+and an optional CS# pin.
 
+If CS# is supplied, data is only decoded when CS# is asserted (clock
+transitions where CS# is not asserted are ignored). If CS# is not supplied,
+data is decoded on every clock transition (depending on SPI mode).
 '''
 
 from .pd import *
diff --git a/decoders/spi/pd.py b/decoders/spi/pd.py
index b6c96bc..7e4a1e5 100644
--- a/decoders/spi/pd.py
+++ b/decoders/spi/pd.py
@@ -23,6 +23,26 @@
 
 import sigrokdecode as srd
 
+'''
+Protocol output format:
+
+SPI packet:
+[<cmd>, <data1>, <data2>]
+
+Commands:
+ - 'DATA': <data1> contains the MISO data, <data2> contains the MOSI data.
+   The data is _usually_ 8 bits (but can also be fewer or more bits).
+   Both data items are Python numbers, not strings.
+ - 'CS CHANGE': <data1> is the old CS# pin value, <data2> is the new value.
+   Both data items are Python numbers (0/1), not strings.
+
+Examples:
+ ['CS-CHANGE', 1, 0]
+ ['DATA', 0xff, 0x3a]
+ ['DATA', 0x65, 0x00]
+ ['CS-CHANGE', 0, 1]
+'''
+
 # Key: (CPOL, CPHA). Value: SPI mode.
 # Clock polarity (CPOL) = 0/1: Clock is low/high when inactive.
 # Clock phase (CPHA) = 0/1: Data is valid on the leading/trailing clock edge.