X-Git-Url: https://sigrok.org/gitweb/?a=blobdiff_plain;f=decoders%2Fuart%2Fuart.py;h=16048346d1bd70d06053fd5dc4b07a4dd766f003;hb=a7fc4c342689ab3b42cd8e662612e12aee8a2bf3;hp=5098977cc074e3d841cc39c9edcd9224a146ce02;hpb=1ccef4616d2c6d6fcdfee6a72d051387625678ca;p=libsigrokdecode.git diff --git a/decoders/uart/uart.py b/decoders/uart/uart.py index 5098977..1604834 100644 --- a/decoders/uart/uart.py +++ b/decoders/uart/uart.py @@ -22,101 +22,6 @@ # 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: -# [, , ] -# -# This is the list of s and their respective : -# - 'STARTBIT': The data is the (integer) value of the start bit (0 or 1). -# - '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). -# - 'PARITYBIT': The data is the (integer) value of the parity bit (0 or 1). -# - 'STOPBIT': The data is the (integer) value of the stop bit (0 or 1). -# - 'INVALID STARTBIT': The data is the (integer) value of the start bit -# (0 or 1). -# - 'INVALID STOPBIT': The data is the (integer) value of the stop bit -# (0 or 1). -# - '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. -# - TODO: Frame error? -# -# The field is 0 for RX packets, 1 for TX packets. -# - import sigrokdecode as srd # States @@ -130,23 +35,6 @@ GET_STOP_BITS = 4 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 @@ -157,22 +45,22 @@ ANN_BITS = 4 # 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) @@ -197,10 +85,10 @@ class Decoder(srd.Decoder): 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 = [ @@ -303,15 +191,15 @@ class Decoder(srd.Decoder): 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. @@ -337,7 +225,7 @@ class Decoder(srd.Decoder): 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: + if self.options['parity_type'] == 'none': self.state[rxtx] = GET_STOP_BITS return @@ -367,7 +255,7 @@ class Decoder(srd.Decoder): # 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