##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
## Copyright (C) 2012-2013 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
##
# SPI protocol decoder
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.
spi_mode = {
(0, 0): 0, # Mode 0
(0, 1): 1, # Mode 1
(1, 0): 2, # Mode 2
(1, 1): 3, # Mode 3
}
class Decoder(srd.Decoder):
api_version = 1
id = 'spi'
name = 'SPI'
longname = 'Serial Peripheral Interface'
desc = 'Full-duplex, synchronous, serial bus.'
license = 'gplv2+'
inputs = ['logic']
outputs = ['spi']
probes = [
{'id': 'miso', 'name': 'MISO',
'desc': 'SPI MISO line (Master in, slave out)'},
{'id': 'mosi', 'name': 'MOSI',
'desc': 'SPI MOSI line (Master out, slave in)'},
{'id': 'sck', 'name': 'CLK', 'desc': 'SPI clock line'},
]
optional_probes = [
{'id': 'cs', 'name': 'CS#', 'desc': 'SPI chip-select line'},
]
options = {
'cs_polarity': ['CS# polarity', 'active-low'],
'cpol': ['Clock polarity', 0],
'cpha': ['Clock phase', 0],
'bitorder': ['Bit order within the SPI data', 'msb-first'],
'wordsize': ['Word size of SPI data', 8], # 1-64?
'format': ['Data format', 'hex'],
}
annotations = [
['MISO/MOSI data', 'MISO/MOSI SPI data'],
['MISO data', 'MISO SPI data'],
['MOSI data', 'MOSI SPI data'],
['Warnings', 'Human-readable warnings'],
]
def __init__(self):
self.oldsck = 1
self.bitcount = 0
self.mosidata = 0
self.misodata = 0
self.bytesreceived = 0
self.startsample = -1
self.samplenum = -1
self.cs_was_deasserted_during_data_word = 0
self.oldcs = -1
self.oldpins = None
self.state = 'IDLE'
def start(self, metadata):
self.out_proto = self.add(srd.OUTPUT_PROTO, 'spi')
self.out_ann = self.add(srd.OUTPUT_ANN, 'spi')
def report(self):
return 'SPI: %d bytes received' % self.bytesreceived
def putpw(self, data):
self.put(self.startsample, self.samplenum, self.out_proto, data)
def putw(self, data):
self.put(self.startsample, self.samplenum, self.out_ann, data)
def handle_bit(self, miso, mosi, sck, cs):
# If this is the first bit, save its sample number.
if self.bitcount == 0:
self.startsample = self.samplenum
if self.have_cs:
active_low = (self.options['cs_polarity'] == 'active-low')
deasserted = cs if active_low else not cs
if deasserted:
self.cs_was_deasserted_during_data_word = 1
ws = self.options['wordsize']
# Receive MOSI bit into our shift register.
if self.options['bitorder'] == 'msb-first':
self.mosidata |= mosi << (ws - 1 - self.bitcount)
else:
self.mosidata |= mosi << self.bitcount
# Receive MISO bit into our shift register.
if self.options['bitorder'] == 'msb-first':
self.misodata |= miso << (ws - 1 - self.bitcount)
else:
self.misodata |= miso << self.bitcount
self.bitcount += 1
# Continue to receive if not enough bits were received, yet.
if self.bitcount != ws:
return
self.putpw(['DATA', self.mosidata, self.misodata])
self.putw([0, ['%02X/%02X' % (self.mosidata, self.misodata)]])
self.putw([1, ['%02X' % self.misodata]])
self.putw([2, ['%02X' % self.mosidata]])
if self.cs_was_deasserted_during_data_word:
self.putw([3, ['CS# was deasserted during this data word!']])
# Reset decoder state.
self.mosidata = self.misodata = self.bitcount = 0
# Keep stats for summary.
self.bytesreceived += 1
def find_clk_edge(self, miso, mosi, sck, cs):
if self.have_cs and self.oldcs != cs:
# Send all CS# pin value changes.
self.put(self.samplenum, self.samplenum, self.out_proto,
['CS-CHANGE', self.oldcs, cs])
self.oldcs = cs
# Reset decoder state when CS# changes (and the CS# pin is used).
self.mosidata = self.misodata = self.bitcount= 0
# Ignore sample if the clock pin hasn't changed.
if sck == self.oldsck:
return
self.oldsck = sck
# Sample data on rising/falling clock edge (depends on mode).
mode = spi_mode[self.options['cpol'], self.options['cpha']]
if mode == 0 and sck == 0: # Sample on rising clock edge
return
elif mode == 1 and sck == 1: # Sample on falling clock edge
return
elif mode == 2 and sck == 1: # Sample on falling clock edge
return
elif mode == 3 and sck == 0: # Sample on rising clock edge
return
# Found the correct clock edge, now get the SPI bit(s).
self.handle_bit(miso, mosi, sck, cs)
def decode(self, ss, es, data):
# TODO: Either MISO or MOSI could be optional. CS# is optional.
for (self.samplenum, pins) in data:
# Ignore identical samples early on (for performance reasons).
if self.oldpins == pins:
continue
self.oldpins, (miso, mosi, sck, cs) = pins, pins
self.have_cs = (cs in (0, 1))
# State machine.
if self.state == 'IDLE':
self.find_clk_edge(miso, mosi, sck, cs)
else:
raise Exception('Invalid state: %s' % self.state)