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-rw-r--r--decoders/uart/pd.py16
1 files changed, 10 insertions, 6 deletions
diff --git a/decoders/uart/pd.py b/decoders/uart/pd.py
index 4ce6ef9..9ffcb56 100644
--- a/decoders/uart/pd.py
+++ b/decoders/uart/pd.py
@@ -114,6 +114,7 @@ class Decoder(srd.Decoder):
'values': ('yes', 'no')},
{'id': 'invert_tx', 'desc': 'Invert TX', 'default': 'no',
'values': ('yes', 'no')},
+ {'id': 'sample_point', 'desc': 'Sample point (%)', 'default': 50},
{'id': 'rx_packet_delim', 'desc': 'RX packet delimiter (decimal)',
'default': -1},
{'id': 'tx_packet_delim', 'desc': 'TX packet delimiter (decimal)',
@@ -224,12 +225,15 @@ class Decoder(srd.Decoder):
def get_sample_point(self, rxtx, bitnum):
# Determine absolute sample number of a bit slot's sample point.
- # bitpos is the samplenumber which is in the middle of the
- # specified UART bit (0 = start bit, 1..x = data, x+1 = parity bit
- # (if used) or the first stop bit, and so on).
- # The samples within bit are 0, 1, ..., (bit_width - 1), therefore
- # index of the middle sample within bit window is (bit_width - 1) / 2.
- bitpos = self.frame_start[rxtx] + (self.bit_width - 1) / 2.0
+ # Counts for UART bits start from 0 (0 = start bit, 1..x = data,
+ # x+1 = parity bit (if used) or the first stop bit, and so on).
+ # Accept a position in the range of 1.99% of the full bit width.
+ # Assume 50% for invalid input specs for backwards compatibility.
+ perc = self.options['sample_point'] or 50
+ if not perc or perc not in range(1, 100):
+ perc = 50
+ bitpos = (self.bit_width - 1) * perc / 100
+ bitpos += self.frame_start[rxtx]
bitpos += bitnum * self.bit_width
return bitpos