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Diffstat (limited to 'decoders/onewire_transport/__init__.py')
| -rw-r--r-- | decoders/onewire_transport/__init__.py | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/decoders/onewire_transport/__init__.py b/decoders/onewire_transport/__init__.py new file mode 100644 index 0000000..28db017 --- /dev/null +++ b/decoders/onewire_transport/__init__.py @@ -0,0 +1,76 @@ +## +## This file is part of the sigrok project. +## +## Copyright (C) 2012 Uwe Hermann <uwe@hermann-uwe.de> +## +## This program is free software; you can redistribute it and/or modify +## it under the terms of the GNU General Public License as published by +## the Free Software Foundation; either version 2 of the License, or +## (at your option) any later version. +## +## This program is distributed in the hope that it will be useful, +## but WITHOUT ANY WARRANTY; without even the implied warranty of +## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +## GNU General Public License for more details. +## +## You should have received a copy of the GNU General Public License +## along with this program; if not, write to the Free Software +## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA +## + +''' +1-Wire protocol decoder. + +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_transport import * |