## ## This file is part of the libsigrokdecode project. ## ## Copyright (C) 2010-2014 Uwe Hermann ## ## 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 ## # TODO: Look into arbitration, collision detection, clock synchronisation, etc. # TODO: Implement support for 10bit slave addresses. # TODO: Implement support for inverting SDA/SCL levels (0->1 and 1->0). # TODO: Implement support for detecting various bus errors. import sigrokdecode as srd ''' OUTPUT_PYTHON format: I²C packet: [, ] is one of: - 'START' (START condition) - 'START REPEAT' (Repeated START condition) - 'ADDRESS READ' (Slave address, read) - 'ADDRESS WRITE' (Slave address, write) - 'DATA READ' (Data, read) - 'DATA WRITE' (Data, write) - 'STOP' (STOP condition) - 'ACK' (ACK bit) - 'NACK' (NACK bit) - 'BITS' (: list of data/address bits and their ss/es numbers) is the data or address byte associated with the 'ADDRESS*' and 'DATA*' command. Slave addresses do not include bit 0 (the READ/WRITE indication bit). For example, a slave address field could be 0x51 (instead of 0xa2). For 'START', 'START REPEAT', 'STOP', 'ACK', and 'NACK' is None. ''' # CMD: [annotation-type-index, long annotation, short annotation] proto = { 'START': [0, 'Start', 'S'], 'START REPEAT': [1, 'Start repeat', 'Sr'], 'STOP': [2, 'Stop', 'P'], 'ACK': [3, 'ACK', 'A'], 'NACK': [4, 'NACK', 'N'], 'BIT': [5, 'Bit', 'B'], 'ADDRESS READ': [6, 'Address read', 'AR'], 'ADDRESS WRITE': [7, 'Address write', 'AW'], 'DATA READ': [8, 'Data read', 'DR'], 'DATA WRITE': [9, 'Data write', 'DW'], } class Decoder(srd.Decoder): api_version = 2 id = 'i2c' name = 'I²C' longname = 'Inter-Integrated Circuit' desc = 'Two-wire, multi-master, serial bus.' license = 'gplv2+' inputs = ['logic'] outputs = ['i2c'] channels = ( {'id': 'scl', 'name': 'SCL', 'desc': 'Serial clock line'}, {'id': 'sda', 'name': 'SDA', 'desc': 'Serial data line'}, ) options = ( {'id': 'address_format', 'desc': 'Displayed slave address format', 'default': 'shifted', 'values': ('shifted', 'unshifted')}, ) annotations = ( ('start', 'Start condition'), ('repeat-start', 'Repeat start condition'), ('stop', 'Stop condition'), ('ack', 'ACK'), ('nack', 'NACK'), ('bit', 'Data/address bit'), ('address-read', 'Address read'), ('address-write', 'Address write'), ('data-read', 'Data read'), ('data-write', 'Data write'), ('warnings', 'Human-readable warnings'), ) annotation_rows = ( ('bits', 'Bits', (5,)), ('addr-data', 'Address/Data', (0, 1, 2, 3, 4, 6, 7, 8, 9)), ('warnings', 'Warnings', (10,)), ) binary = ( ('address-read', 'Address read'), ('address-write', 'Address write'), ('data-read', 'Data read'), ('data-write', 'Data write'), ) def __init__(self, **kwargs): self.samplerate = None self.ss = self.es = self.byte_ss = -1 self.samplenum = None self.bitcount = 0 self.databyte = 0 self.wr = -1 self.is_repeat_start = 0 self.state = 'FIND START' self.oldscl = self.oldsda = 1 self.oldpins = [1, 1] self.pdu_start = None self.pdu_bits = 0 self.bits = [] def metadata(self, key, value): if key == srd.SRD_CONF_SAMPLERATE: self.samplerate = value def start(self): self.out_python = self.register(srd.OUTPUT_PYTHON) self.out_ann = self.register(srd.OUTPUT_ANN) self.out_binary = self.register(srd.OUTPUT_BINARY) self.out_bitrate = self.register(srd.OUTPUT_META, meta=(int, 'Bitrate', 'Bitrate from Start bit to Stop bit')) def putx(self, data): self.put(self.ss, self.es, self.out_ann, data) def putp(self, data): self.put(self.ss, self.es, self.out_python, data) def putb(self, data): self.put(self.ss, self.es, self.out_binary, data) def is_start_condition(self, scl, sda): # START condition (S): SDA = falling, SCL = high if (self.oldsda == 1 and sda == 0) and scl == 1: return True return False def is_data_bit(self, scl, sda): # Data sampling of receiver: SCL = rising if self.oldscl == 0 and scl == 1: return True return False def is_stop_condition(self, scl, sda): # STOP condition (P): SDA = rising, SCL = high if (self.oldsda == 0 and sda == 1) and scl == 1: return True return False def found_start(self, scl, sda): self.ss, self.es = self.samplenum, self.samplenum self.pdu_start = self.samplenum self.pdu_bits = 0 cmd = 'START REPEAT' if (self.is_repeat_start == 1) else 'START' self.putp([cmd, None]) self.putx([proto[cmd][0], proto[cmd][1:]]) self.state = 'FIND ADDRESS' self.bitcount = self.databyte = 0 self.is_repeat_start = 1 self.wr = -1 self.bits = [] # Gather 8 bits of data plus the ACK/NACK bit. def found_address_or_data(self, scl, sda): # Address and data are transmitted MSB-first. self.databyte <<= 1 self.databyte |= sda # Remember the start of the first data/address bit. if self.bitcount == 0: self.byte_ss = self.samplenum # Store individual bits and their start/end samplenumbers. # In the list, index 0 represents the LSB (I²C transmits MSB-first). self.bits.insert(0, [sda, self.samplenum, self.samplenum]) if self.bitcount > 0: self.bits[1][2] = self.samplenum if self.bitcount == 7: self.bitwidth = self.bits[1][2] - self.bits[2][2] self.bits[0][2] += self.bitwidth # Return if we haven't collected all 8 + 1 bits, yet. if self.bitcount < 7: self.bitcount += 1 return d = self.databyte if self.state == 'FIND ADDRESS': # The READ/WRITE bit is only in address bytes, not data bytes. self.wr = 0 if (self.databyte & 1) else 1 if self.options['address_format'] == 'shifted': d = d >> 1 bin_class = -1 if self.state == 'FIND ADDRESS' and self.wr == 1: cmd = 'ADDRESS WRITE' bin_class = 1 elif self.state == 'FIND ADDRESS' and self.wr == 0: cmd = 'ADDRESS READ' bin_class = 0 elif self.state == 'FIND DATA' and self.wr == 1: cmd = 'DATA WRITE' bin_class = 3 elif self.state == 'FIND DATA' and self.wr == 0: cmd = 'DATA READ' bin_class = 2 self.ss, self.es = self.byte_ss, self.samplenum + self.bitwidth self.putp(['BITS', self.bits]) self.putp([cmd, d]) self.putb((bin_class, bytes([d]))) for bit in self.bits: self.put(bit[1], bit[2], self.out_ann, [5, ['%d' % bit[0]]]) if cmd.startswith('ADDRESS'): self.ss, self.es = self.samplenum, self.samplenum + self.bitwidth w = ['Write', 'Wr', 'W'] if self.wr else ['Read', 'Rd', 'R'] self.putx([proto[cmd][0], w]) self.ss, self.es = self.byte_ss, self.samplenum self.putx([proto[cmd][0], ['%s: %02X' % (proto[cmd][1], d), '%s: %02X' % (proto[cmd][2], d), '%02X' % d]]) # Done with this packet. self.bitcount = self.databyte = 0 self.bits = [] self.state = 'FIND ACK' def get_ack(self, scl, sda): self.ss, self.es = self.samplenum, self.samplenum + self.bitwidth cmd = 'NACK' if (sda == 1) else 'ACK' self.putp([cmd, None]) self.putx([proto[cmd][0], proto[cmd][1:]]) # There could be multiple data bytes in a row, so either find # another data byte or a STOP condition next. self.state = 'FIND DATA' def found_stop(self, scl, sda): # Meta bitrate elapsed = 1 / float(self.samplerate) * (self.samplenum - self.pdu_start + 1) bitrate = int(1 / elapsed * self.pdu_bits) self.put(self.byte_ss, self.samplenum, self.out_bitrate, bitrate) cmd = 'STOP' self.ss, self.es = self.samplenum, self.samplenum self.putp([cmd, None]) self.putx([proto[cmd][0], proto[cmd][1:]]) self.state = 'FIND START' self.is_repeat_start = 0 self.wr = -1 self.bits = [] def decode(self, ss, es, data): if self.samplerate is None: raise Exception("Cannot decode without samplerate.") for (self.samplenum, pins) in data: # Ignore identical samples early on (for performance reasons). if self.oldpins == pins: continue self.oldpins, (scl, sda) = pins, pins self.pdu_bits += 1 # State machine. if self.state == 'FIND START': if self.is_start_condition(scl, sda): self.found_start(scl, sda) elif self.state == 'FIND ADDRESS': if self.is_data_bit(scl, sda): self.found_address_or_data(scl, sda) elif self.state == 'FIND DATA': if self.is_data_bit(scl, sda): self.found_address_or_data(scl, sda) elif self.is_start_condition(scl, sda): self.found_start(scl, sda) elif self.is_stop_condition(scl, sda): self.found_stop(scl, sda) elif self.state == 'FIND ACK': if self.is_data_bit(scl, sda): self.get_ack(scl, sda) else: raise Exception('Invalid state: %s' % self.state) # Save current SDA/SCL values for the next round. self.oldscl, self.oldsda = scl, sda