decoders/spi.py

   1 class Sample():
   2         def __init__(self, data):
   3                 self.data = data
   4         def probe(self, probe):
   5                 s = ord(self.data[probe / 8]) & (1 << (probe % 8))
   6                 return True if s else False
   7
   8 def sampleiter(data, unitsize):
   9         for i in range(0, len(data), unitsize):
  10                 yield(Sample(data[i:i+unitsize]))
  11
  12 class Decoder():
  13         # Probe names with a set of defaults
  14         probes = {'sdata':0, 'sck':1}
  15
  16         def __init__(self, metadata, **kwargs):
  17                 # Metadata comes in here, we don't care for now
  18                 #print kwargs
  19                 self.unitsize = metadata['unitsize']
  20
  21                 self.probes = Decoder.probes
  22                 self.oldsck = True
  23                 self.rxcount = 0
  24                 self.rxdata = 0
  25                 self.bytesreceived = 0
  26
  27         def summary(self):
  28                 return "SPI: %d bytes received" % self.bytesreceived
  29
  30         def decode(self, data):
  31                 # We should accept a list of samples and iterate...
  32                 for sample in sampleiter(data["data"], self.unitsize):
  33
  34                         sck = sample.probe(self.probes["sck"])
  35                         # Sample SDATA on rising SCK
  36                         if sck == self.oldsck:
  37                                 continue
  38                         self.oldsck = sck
  39                         if not sck:
  40                                 continue
  41
  42                         # If this is first bit, save timestamp
  43                         if self.rxcount == 0:
  44                                 self.time = data["time"]
  45                         # Receive bit into our shift register
  46                         sdata = sample.probe(self.probes["sdata"])
  47                         if sdata:
  48                                 self.rxdata |= 1 << (7 - self.rxcount)
  49                         self.rxcount += 1
  50                         # Continue to receive if not a byte yet
  51                         if self.rxcount != 8:
  52                                 continue
  53                         # Received a byte, pass up to sigrok
  54                         outdata = {"time":self.time,
  55                                 "duration":data["time"] + data["duration"] - self.time,
  56                                 "data":self.rxdata,
  57                                 "display":("%02X" % self.rxdata),
  58                                 "type":"spi",
  59                         }
  60                         print outdata
  61                         sigrok.put(outdata)
  62                         # Reset decoder state
  63                         self.rxdata = 0
  64                         self.rxcount = 0
  65                         # Keep stats for summary
  66                         self.bytesreceived += 1
  67
  68
  69 register = {
  70         'id': 'spi',
  71         'name': 'SPI Decoder',
  72         'longname': '...',
  73         'desc': 'Decodes SPI frames',
  74         'longdesc': '...',
  75         'author': 'Gareth McMullin',
  76         'email': 'gareth@blacksphere.co.nz',
  77         'license': 'gplv2+',
  78         'in': ['logic'],
  79         'out': ['spi'],
  80         'probes': [
  81                 # All probes.
  82         ],
  83         'options': {
  84                 # No options so far.
  85         },
  86         # 'start': start,
  87         # 'report': report,
  88 }
  89
  90 if __name__ == "__main__":
  91         data = open("spi_dump.bin").read()
  92
  93         # dummy class to keep Decoder happy for test
  94         class Sigrok():
  95                 def put(self, data):
  96                         print "\t", data
  97         sigrok = Sigrok()
  98
  99         dec = Decoder(driver='ols', unitsize=1, starttime=0)
 100         dec.decode({"time":0, "duration":len(data), "data":data, "type":"logic"})
 101
 102         print dec.summary()
 103 else:
 104         import sigrok
 105
 106 #Tested with:
 107 #  sigrok-cli -d 0:samplerate=1000000:rle=on --time=1s -p 1,2 -a spidec
 108
 109