diff options
| -rw-r--r-- | decoders/spi.py | 43 |
1 files changed, 30 insertions, 13 deletions
diff --git a/decoders/spi.py b/decoders/spi.py index 7c56aed..480174e 100644 --- a/decoders/spi.py +++ b/decoders/spi.py @@ -37,6 +37,13 @@ CPHA_1 = 1 # Data is valid on the falling clock edge MSB_FIRST = 0 LSB_FIRST = 1 +spi_mode = { + (0, 0): 0, # Mode 0 + (0, 1): 1, # Mode 1 + (1, 0): 2, # Mode 2 + (1, 1): 3, # Mode 3 +} + # Annotation formats ANN_HEX = 0 @@ -61,10 +68,10 @@ class Decoder(srd.Decoder): ] options = { 'cs_active_low': ['CS# active low', ACTIVE_LOW], - 'clock_polarity': ['Clock polarity', CPOL_0], - 'clock_phase': ['Clock phase', CPHA_0], - 'bit_order': ['Bit order within the SPI data', MSB_FIRST], - 'word_size': ['Word size of SPI data', 8], # 1-64? + 'cpol': ['Clock polarity', CPOL_0], + 'cpha': ['Clock phase', CPHA_0], + 'bitorder': ['Bit order within the SPI data', MSB_FIRST], + 'wordsize': ['Word size of SPI data', 8], # 1-64? } annotations = [ ['Hex', 'SPI data bytes in hex format'], @@ -80,10 +87,10 @@ class Decoder(srd.Decoder): # Set protocol decoder option defaults. self.cs_active_low = Decoder.options['cs_active_low'][1] - self.clock_polarity = Decoder.options['clock_polarity'][1] - self.clock_phase = Decoder.options['clock_phase'][1] - self.bit_order = Decoder.options['bit_order'][1] - self.word_size = Decoder.options['word_size'][1] + self.cpol = Decoder.options['cpol'][1] + self.cpha = Decoder.options['cpha'][1] + self.bitorder = Decoder.options['bitorder'][1] + self.wordsize = Decoder.options['wordsize'][1] def start(self, metadata): self.out_proto = self.add(srd.OUTPUT_PROTO, 'spi') @@ -101,25 +108,35 @@ class Decoder(srd.Decoder): self.samplenum += 1 # FIXME - # Sample data on rising SCK edges. + # Ignore sample if the clock pin hasn't changed. if sck == self.oldsck: continue + self.oldsck = sck - if sck == 0: - continue + + # Sample data on rising/falling clock edge (depends on mode). + mode = spi_mode[self.cpol, self.cpha] + if mode == 0 and sck == 0: # Sample on rising clock edge + continue + elif mode == 1 and sck == 1: # Sample on falling clock edge + continue + elif mode == 2 and sck == 1: # Sample on falling clock edge + continue + elif mode == 3 and sck == 0: # Sample on rising clock edge + continue # If this is the first bit, save its sample number. if self.bitcount == 0: self.start_sample = samplenum # Receive MOSI bit into our shift register. - if self.bit_order == MSB_FIRST: + if self.bitorder == MSB_FIRST: self.mosidata |= mosi << (self.wordsize - 1 - self.bitcount) else: self.mosidata |= mosi << self.bitcount # Receive MISO bit into our shift register. - if self.bit_order == MSB_FIRST: + if self.bitorder == MSB_FIRST: self.misodata |= miso << (self.wordsize - 1 - self.bitcount) else: self.misodata |= miso << self.bitcount |