srd: lm75: Warn about temperature reg. being read-only.

[libsigrokdecode.git] / decoders / onewire / __init__.py

diff --git a/decoders/onewire/__init__.py b/decoders/onewire/__init__.py
index 6fa82989e49df2d2a0c3ada4792a2c30c0e73444..c43dabc4184dd9eb38471a82af7e78005f3d91f0 100644 (file)
--- a/decoders/onewire/__init__.py
+++ b/decoders/onewire/__init__.py
@@ -21,7 +21,56 @@
 '''
 1-Wire protocol decoder.
 
-TODO.
+The 1-Wire protocol enables bidirectional communication over a single wire (and
+ground) between a single master and one or multiple slaves. The protocol is
+layered, the provided parser decodes the next layers:
+- Link layer (reset, presence detection, reading/writing bits)
+- Network layer (skip, search, match device ROM addresses)
+The higher layers (transport, presentation) are not decoded, since they are
+mostly device specific and it would take a lot of code to interpret them.
+
+Sample rate:
+A high enough sample rate is required to properly detect all the elements of
+the protocol. A lower sample rate can be used if the master does not use
+overdrive communication speed. The next minimal values should be used:
+- overdrive     available:   2MHz minimum, 5MHz suggested
+- overdrive not available: 400kHz minimum, 1MHz suggested
+
+Probes:
+1-Wire requires a single signal, but some master implementations might have a
+separate signal use to deliver power to the bus during temperature conversion
+as an example. This power signal is currently not parsed.
+- owr (1-Wire bus)
+- pwr (1-Wire power)
+
+Options:
+1-Wire is an asynchronous protocol, so the decoder must know the sample rate.
+The timing for sampling bits, presence and reset is calculated by the decoder,
+but in case the user wishes to use different values, it is possible to
+configure the next timing values (number of sample rate periods):
+- overdrive              (if active the decoder will be prepared for overdrive)
+- cnt_normal_bit         (time for normal mode sample bit)
+- cnt_normal_presence    (time for normal mode sample presence)
+- cnt_normal_reset       (time for normal mode reset)
+- cnt_overdrive_bit      (time for overdrive mode sample bit)
+- cnt_overdrive_presence (time for overdrive mode sample presence)
+- cnt_overdrive_reset    (time for overdrive mode reset)
+This options should be configured only on very rare cases and the user should
+read the decoder source code to understand them correctly.
+
+Annotations:
+Annotations can be shown for each layer of the protocol separately:
+- link (the value of each transmitted bit is shown separately)
+- network (the ROM command, and address are shown)
+- transport (only transport layer byte transfers are shown)
+If link layer annotations are shown, possible issues with sample rate and sample
+timing are also shown.
+
+TODO:
+- add CRC checks for network layer
+- add transport layer code
+- review link layer code, to check for protocol correctness
+- define output protocol
 '''
 
 from .onewire import *