## Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
##
-#
# UART protocol decoder
-#
-
-#
-# Universal Asynchronous Receiver Transmitter (UART) is a simple serial
-# communication protocol which allows two devices to talk to each other.
-#
-# It uses just two data signals and a ground (GND) signal:
-# - RX/RXD: Receive signal
-# - TX/TXD: Transmit signal
-#
-# The protocol is asynchronous, i.e., there is no dedicated clock signal.
-# Rather, both devices have to agree on a baudrate (number of bits to be
-# transmitted per second) beforehand. Baudrates can be arbitrary in theory,
-# but usually the choice is limited by the hardware UARTs that are used.
-# Common values are 9600 or 115200.
-#
-# The protocol allows full-duplex transmission, i.e. both devices can send
-# data at the same time. However, unlike SPI (which is always full-duplex,
-# i.e., each send operation is automatically also a receive operation), UART
-# allows one-way communication, too. In such a case only one signal (and GND)
-# is required.
-#
-# The data is sent over the TX line in so-called 'frames', which consist of:
-# - Exactly one start bit (always 0/low).
-# - Between 5 and 9 data bits.
-# - An (optional) parity bit.
-# - One or more stop bit(s).
-#
-# The idle state of the RX/TX line is 1/high. As the start bit is 0/low, the
-# receiver can continually monitor its RX line for a falling edge, in order
-# to detect the start bit.
-#
-# Once detected, it can (due to the agreed-upon baudrate and thus the known
-# width/duration of one UART bit) sample the state of the RX line "in the
-# middle" of each (start/data/parity/stop) bit it wants to analyze.
-#
-# It is configurable whether there is a parity bit in a frame, and if yes,
-# which type of parity is used:
-# - None: No parity bit is included.
-# - Odd: The number of 1 bits in the data (and parity bit itself) is odd.
-# - Even: The number of 1 bits in the data (and parity bit itself) is even.
-# - Mark/one: The parity bit is always 1/high (also called 'mark state').
-# - Space/zero: The parity bit is always 0/low (also called 'space state').
-#
-# It is also configurable how many stop bits are to be used:
-# - 1 stop bit (most common case)
-# - 2 stop bits
-# - 1.5 stop bits (i.e., one stop bit, but 1.5 times the UART bit width)
-# - 0.5 stop bits (i.e., one stop bit, but 0.5 times the UART bit width)
-#
-# The bit order of the 5-9 data bits is LSB-first.
-#
-# Possible special cases:
-# - One or both data lines could be inverted, which also means that the idle
-# state of the signal line(s) is low instead of high.
-# - Only the data bits on one or both data lines (and the parity bit) could
-# be inverted (but the start/stop bits remain non-inverted).
-# - The bit order could be MSB-first instead of LSB-first.
-# - The baudrate could change in the middle of the communication. This only
-# happens in very special cases, and can only work if both devices know
-# to which baudrate they are to switch, and when.
-# - Theoretically, the baudrate on RX and the one on TX could also be
-# different, but that's a very obscure case and probably doesn't happen
-# very often in practice.
-#
-# Error conditions:
-# - If there is a parity bit, but it doesn't match the expected parity,
-# this is called a 'parity error'.
-# - If there are no stop bit(s), that's called a 'frame error'.
-#
-# More information:
-# TODO: URLs
-#
-
-#
-# Protocol output format:
-#
-# UART packet:
-# [<packet-type>, <rxtx>, <packet-data>]
-#
-# This is the list of <packet-types>s and their respective <packet-data>:
-# - T_START: The data is the (integer) value of the start bit (0 or 1).
-# - T_DATA: The data is the (integer) value of the UART data. Valid values
-# range from 0 to 512 (as the data can be up to 9 bits in size).
-# - T_PARITY: The data is the (integer) value of the parity bit (0 or 1).
-# - T_STOP: The data is the (integer) value of the stop bit (0 or 1).
-# - T_INVALID_START: The data is the (integer) value of the start bit (0 or 1).
-# - T_INVALID_STOP: The data is the (integer) value of the stop bit (0 or 1).
-# - T_PARITY_ERROR: The data is a tuple with two entries. The first one is
-# the expected parity value, the second is the actual parity value.
-#
-# The <rxtx> field is 0 for RX packets, 1 for TX packets.
-#
import sigrokdecode as srd
-# States
-WAIT_FOR_START_BIT = 0
-GET_START_BIT = 1
-GET_DATA_BITS = 2
-GET_PARITY_BIT = 3
-GET_STOP_BITS = 4
-
# Used for differentiating between the two data directions.
RX = 0
TX = 1
-# Parity options
-PARITY_NONE = 0
-PARITY_ODD = 1
-PARITY_EVEN = 2
-PARITY_ZERO = 3
-PARITY_ONE = 4
-
-# Stop bit options
-STOP_BITS_0_5 = 0
-STOP_BITS_1 = 1
-STOP_BITS_1_5 = 2
-STOP_BITS_2 = 3
-
-# Bit order options
-LSB_FIRST = 0
-MSB_FIRST = 1
-
# Annotation feed formats
ANN_ASCII = 0
ANN_DEC = 1
ANN_OCT = 3
ANN_BITS = 4
-# Protocol output packet types
-T_START = 0
-T_DATA = 1
-T_PARITY = 2
-T_STOP = 3
-T_INVALID_START = 4
-T_INVALID_STOP = 5
-T_PARITY_ERROR = 6
-
# Given a parity type to check (odd, even, zero, one), the value of the
# parity bit, the value of the data, and the length of the data (5-9 bits,
# usually 8 bits) return True if the parity is correct, False otherwise.
-# PARITY_NONE is _not_ allowed as value for 'parity_type'.
+# 'none' is _not_ allowed as value for 'parity_type'.
def parity_ok(parity_type, parity_bit, data, num_data_bits):
# Handle easy cases first (parity bit is always 1 or 0).
- if parity_type == PARITY_ZERO:
+ if parity_type == 'zero':
return parity_bit == 0
- elif parity_type == PARITY_ONE:
+ elif parity_type == 'one':
return parity_bit == 1
# Count number of 1 (high) bits in the data (and the parity bit itself!).
ones = bin(data).count('1') + parity_bit
# Check for odd/even parity.
- if parity_type == PARITY_ODD:
+ if parity_type == 'odd':
return (ones % 2) == 1
- elif parity_type == PARITY_EVEN:
+ elif parity_type == 'even':
return (ones % 2) == 0
else:
raise Exception('Invalid parity type: %d' % parity_type)
options = {
'baudrate': ['Baud rate', 115200],
'num_data_bits': ['Data bits', 8], # Valid: 5-9.
- 'parity_type': ['Parity type', PARITY_NONE],
- 'parity_check': ['Check parity?', True], # TODO: Bool supported?
- 'num_stop_bits': ['Stop bit(s)', STOP_BITS_1],
- 'bit_order': ['Bit order', LSB_FIRST],
+ 'parity_type': ['Parity type', 'none'],
+ 'parity_check': ['Check parity?', 'yes'], # TODO: Bool supported?
+ 'num_stop_bits': ['Stop bit(s)', '1'], # String! 0, 0.5, 1, 1.5.
+ 'bit_order': ['Bit order', 'lsb-first'],
# TODO: Options to invert the signal(s).
}
annotations = [
self.startbit = [-1, -1]
self.cur_data_bit = [0, 0]
self.databyte = [0, 0]
+ self.paritybit = [-1, -1]
self.stopbit1 = [-1, -1]
self.startsample = [-1, -1]
# Initial state.
- self.state = [WAIT_FOR_START_BIT, WAIT_FOR_START_BIT]
+ self.state = ['WAIT FOR START BIT', 'WAIT FOR START BIT']
self.oldbit = [None, None]
# Save the sample number where the start bit begins.
self.frame_start[rxtx] = self.samplenum
- self.state[rxtx] = GET_START_BIT
+ self.state[rxtx] = 'GET START BIT'
def get_start_bit(self, rxtx, signal):
# Skip samples until we're in the middle of the start bit.
# The startbit must be 0. If not, we report an error.
if self.startbit[rxtx] != 0:
self.put(self.frame_start[rxtx], self.samplenum, self.out_proto,
- [T_INVALID_START, rxtx, self.startbit[rxtx]])
+ ['INVALID STARTBIT', rxtx, self.startbit[rxtx]])
# TODO: Abort? Ignore rest of the frame?
self.cur_data_bit[rxtx] = 0
self.databyte[rxtx] = 0
self.startsample[rxtx] = -1
- self.state[rxtx] = GET_DATA_BITS
+ self.state[rxtx] = 'GET DATA BITS'
self.put(self.frame_start[rxtx], self.samplenum, self.out_proto,
- [T_START, rxtx, self.startbit[rxtx]])
+ ['STARTBIT', rxtx, self.startbit[rxtx]])
self.put(self.frame_start[rxtx], self.samplenum, self.out_ann,
[ANN_ASCII, ['Start bit', 'Start', 'S']])
self.startsample[rxtx] = self.samplenum
# Get the next data bit in LSB-first or MSB-first fashion.
- if self.options['bit_order'] == LSB_FIRST:
+ if self.options['bit_order'] == 'lsb-first':
self.databyte[rxtx] >>= 1
self.databyte[rxtx] |= \
(signal << (self.options['num_data_bits'] - 1))
- elif self.options['bit_order'] == MSB_FIRST:
+ elif self.options['bit_order'] == 'msb-first':
self.databyte[rxtx] <<= 1
self.databyte[rxtx] |= (signal << 0)
else:
- raise Exception('Invalid bit order value: %d',
+ raise Exception('Invalid bit order value: %s',
self.options['bit_order'])
# Return here, unless we already received all data bits.
self.cur_data_bit[rxtx] += 1
return
- self.state[rxtx] = GET_PARITY_BIT
+ self.state[rxtx] = 'GET PARITY BIT'
self.put(self.startsample[rxtx], self.samplenum - 1, self.out_proto,
- [T_DATA, rxtx, self.databyte[rxtx]])
+ ['DATA', rxtx, self.databyte[rxtx]])
s = 'RX: ' if (rxtx == RX) else 'TX: '
self.putx(rxtx, [ANN_ASCII, [s + chr(self.databyte[rxtx])]])
def get_parity_bit(self, rxtx, signal):
# If no parity is used/configured, skip to the next state immediately.
- if self.options['parity_type'] == PARITY_NONE:
- self.state[rxtx] = GET_STOP_BITS
+ if self.options['parity_type'] == 'none':
+ self.state[rxtx] = 'GET STOP BITS'
return
# Skip samples until we're in the middle of the parity bit.
self.paritybit[rxtx] = signal
- self.state[rxtx] = GET_STOP_BITS
+ self.state[rxtx] = 'GET STOP BITS'
if parity_ok(self.options['parity_type'], self.paritybit[rxtx],
self.databyte[rxtx], self.options['num_data_bits']):
# TODO: Fix range.
self.put(self.samplenum, self.samplenum, self.out_proto,
- [T_PARITY_BIT, rxtx, self.paritybit[rxtx]])
+ ['PARITYBIT', rxtx, self.paritybit[rxtx]])
self.put(self.samplenum, self.samplenum, self.out_ann,
[ANN_ASCII, ['Parity bit', 'Parity', 'P']])
else:
# TODO: Fix range.
# TODO: Return expected/actual parity values.
self.put(self.samplenum, self.samplenum, self.out_proto,
- [T_PARITY_ERROR, rxtx, (0, 1)]) # FIXME: Dummy tuple...
+ ['PARITY ERROR', rxtx, (0, 1)]) # FIXME: Dummy tuple...
self.put(self.samplenum, self.samplenum, self.out_ann,
[ANN_ASCII, ['Parity error', 'Parity err', 'PE']])
# TODO: Currently only supports 1 stop bit.
def get_stop_bits(self, rxtx, signal):
# Skip samples until we're in the middle of the stop bit(s).
- skip_parity = 0 if self.options['parity_type'] == PARITY_NONE else 1
+ skip_parity = 0 if self.options['parity_type'] == 'none' else 1
b = self.options['num_data_bits'] + 1 + skip_parity
if not self.reached_bit(rxtx, b):
return
# Stop bits must be 1. If not, we report an error.
if self.stopbit1[rxtx] != 1:
self.put(self.frame_start[rxtx], self.samplenum, self.out_proto,
- [T_INVALID_STOP, rxtx, self.stopbit1[rxtx]])
+ ['INVALID STOPBIT', rxtx, self.stopbit1[rxtx]])
# TODO: Abort? Ignore the frame? Other?
- self.state[rxtx] = WAIT_FOR_START_BIT
+ self.state[rxtx] = 'WAIT FOR START BIT'
# TODO: Fix range.
self.put(self.samplenum, self.samplenum, self.out_proto,
- [T_STOP, rxtx, self.stopbit1[rxtx]])
+ ['STOPBIT', rxtx, self.stopbit1[rxtx]])
self.put(self.samplenum, self.samplenum, self.out_ann,
[ANN_ASCII, ['Stop bit', 'Stop', 'P']])
for rxtx in (RX, TX):
signal = rx if (rxtx == RX) else tx
- if self.state[rxtx] == WAIT_FOR_START_BIT:
+ if self.state[rxtx] == 'WAIT FOR START BIT':
self.wait_for_start_bit(rxtx, self.oldbit[rxtx], signal)
- elif self.state[rxtx] == GET_START_BIT:
+ elif self.state[rxtx] == 'GET START BIT':
self.get_start_bit(rxtx, signal)
- elif self.state[rxtx] == GET_DATA_BITS:
+ elif self.state[rxtx] == 'GET DATA BITS':
self.get_data_bits(rxtx, signal)
- elif self.state[rxtx] == GET_PARITY_BIT:
+ elif self.state[rxtx] == 'GET PARITY BIT':
self.get_parity_bit(rxtx, signal)
- elif self.state[rxtx] == GET_STOP_BITS:
+ elif self.state[rxtx] == 'GET STOP BITS':
self.get_stop_bits(rxtx, signal)
else:
raise Exception('Invalid state: %d' % self.state[rxtx])
projects / libsigrokdecode.git / blobdiff