Initial version of sbus

poetry.lock

@@ -0,0 +1,226 @@
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+]

pyproject.toml

@@ -0,0 +1,16 @@
+[tool.poetry]
+name = "sbus"
+version = "0.1.0"
+description = ""
+authors = ["Stan Janssen <stan.janssen@elaad.nl>"]
+
+[tool.poetry.dependencies]
+python = "^3.7"
+pyserial = "^3.4"
+
+[tool.poetry.dev-dependencies]
+pytest = "^5.2"
+
+[build-system]
+requires = ["poetry>=0.12"]
+build-backend = "poetry.masonry.api"

sbus/__init__.py

@@ -0,0 +1,228 @@
+import struct
+import time
+import serial
+from threading import Thread
+
+from .crc import calculate_crc
+
+__version__ = '0.1.0'
+
+# Frame Synchronization
+FS = 0xB5
+
+# Attributes
+AT_REQUEST = 0x00
+AT_RESPONSE = 0x01
+AT_ACK = 0x02
+
+# S-Bus codes
+SC_READ_COUNTER = 0x00
+SC_READ_FLAGS = 0x02
+SC_READ_INPUT = 0x03
+SC_READ_RTC = 0x04
+SC_READ_OUTPUT = 0x05
+SC_READ_REGISTER = 0x06
+SC_READ_TIMER = 0x07
+SC_READ_DATA_BLOCK = 0x96
+SC_WRITE_COUNTER = 0x0A
+SC_WRITE_FLAGS = 0x0B
+SC_WRITE_RTC = 0x0C
+SC_WRITE_OUTPUT = 0x0D
+SC_WRITE_REGISTER = 0x0E
+SC_WRITE_TIMER = 0x0F
+SC_WRITE_DATA_BLOCK = 0x97
+
+REGISTER_SIZE = 4
+MAX_REGISTERS = 10
+REQUEST_SIZE = 9
+
+TIMEOUT = 1.0
+WAIT_BETWEEN_REQUESTS = 0.1
+
+class Instrument:
+    def __init__(self, address, serial_port, timeout=TIMEOUT, **kwargs):
+        self.address = address
+        self.serial = serial.Serial(serial_port, timeout=timeout, **kwargs)
+        self.last_request_time = 0.0
+
+    def read_counter(self, register):
+        raise NotImplementedError("Reading Counters is not yet implemented.")
+
+    def read_flags(self):
+        raise NotImplementedError("Reading Flags is not yet implemented.")
+
+    def read_input(self):
+        raise NotImplementedError("Reading Inputs is not yet implemented.")
+
+    def read_rtc(self):
+        raise NotImplementedError("Reading RTC is not yet implemented.")
+
+    def read_output(self):
+        raise NotImplementedError("Reading Outputs is not yet implemented.")
+
+    def read_register(self, register, num_decimals=0, signed=True):
+        if register > 255:
+            raise ValueError("Maximum value for register is 255")
+        message = [FS, AT_REQUEST, self.address, SC_READ_REGISTER, 0, 0, register]
+        response_size = 4 + 4
+        data = self._perform_request(message, response_size=response_size)
+        return self._interpret_result(data, num_decimals, signed)
+
+    def read_multiple_registers(self, start_register, num_registers=1, num_decimals=0, signed=True):
+        if start_register + num_registers > 255:
+            raise ValueError("Cannot read registers above number 255.")
+        remaining_registers = num_registers
+        results = []
+        while remaining_registers > 0:
+            print(f"Requesting from register {start_register}")
+            num_registers = min(remaining_registers, MAX_REGISTERS)
+
+            message = [FS, AT_REQUEST, self.address, SC_READ_REGISTER, num_registers - 1, 0, start_register]
+            response_size = 4 + 4 * num_registers
+            data = self._perform_request(message, response_size=response_size)
+            results += self._interpret_result(data, num_decimals, signed, always_list=True)
+
+            remaining_registers -= num_registers
+            start_register += num_registers
+        return results
+
+    def read_register_list(self, registers_list, num_decimals=0, signed=True):
+        pass
+
+    def read_mixed_registers_list(self, registers_list, num_decimals_list, signed_list):
+        pass
+
+    def read_timer(self, timer):
+        raise NotImplementedError("Reading Timers is not yet implemented.")
+
+    def read_data_block(self):
+        raise NotImplementedError("Reading Data Blocks is not yet implemented.")
+
+    def write_counter(self):
+        raise NotImplementedError("Writing Counters is not yet implemented.")
+
+    def write_flags(self):
+        raise NotImplementedError("Writing Flags is not yet implemented.")
+
+    def write_rtc(self):
+        raise NotImplementedError("Writing RTC is not yet implemented.")
+
+    def write_output(self):
+        raise NotImplementedError("Writing Outputs is not yet implemented.")
+
+    def write_register(self):
+        raise NotImplementedError("Writing Registers is not yet implemented.")
+
+    def write_timer(self):
+        raise NotImplementedError("Writing Timers is not yet implemented.")
+
+    def write_data_block(self):
+        raise NotImplementedError("Writing Data Blocks is not yet implemented.")
+
+    def _perform_request(self, message, response_size):
+        self._wait_for_next_request()
+        message += calculate_crc(message)
+        self.serial.write(message)
+        response = self.serial.read(response_size)
+        if not response:
+            raise TimeoutError("No response received in time")
+        self._check_crc(response)
+        return response
+
+    def _wait_for_next_request(self):
+        now = time.time()
+        time_elapsed = now - self.last_request_time
+        time.sleep(max(0, WAIT_BETWEEN_REQUESTS - time_elapsed))
+        self.last_request_time = now
+
+    def _check_crc(self, message):
+        crc = calculate_crc(message[:-2])
+        if crc != message[-2:]:
+            return False
+        return True
+
+    def _interpret_result(self, message, num_decimals=0, signed=True, always_list=False):
+        if message[0] != FS:
+            raise ValueError("Message does not begin with byte 0xB5. Check your baudrate and cable polarity.")
+
+        if message[1] != AT_RESPONSE:
+            return _interpret_error(message)
+
+        register_values = []
+        data = message[2:-2]
+        num_registers = int(len(data)/4)
+        if signed:
+            format_code = 'l'
+        else:
+            format_code = 'L'
+        register_values = [value / 10 ** num_decimals for value in struct.unpack(f'>{num_registers}{format_code}', data)]
+
+        if not always_list and len(register_values) == 1:
+            return register_values[0]
+        return register_values
+
+    def _chunk_data(self, data):
+        for i in range(len(data)>>2):
+            yield data[i*REGISTER_SIZE:(i+1)*REGISTER_SIZE]
+
+
+class DeviceEmulator:
+    def __init__(self, address, serial_port, **kwargs):
+        self.serial = serial.Serial(serial_port, **kwargs)
+        self.registers = {}
+        self.thread = None
+
+    def start(self):
+        self.thread = Thread(target=self._run)
+        self.thread.start()
+
+    def stop(self):
+        self.thread.stop()
+
+    def _run(self):
+        while True:
+            byte = self.serial.read(1)
+            if byte != FS:
+                continue
+            request = self._read_message()
+            status, data = self._handle_message(request)
+            response = [FS, status] + data
+            response += calculate_crc(response)
+            self.serial.write(response)
+
+    def _read_message(self):
+        message = FS + self.serial.read(REQUEST_SIZE - 1)
+        if message[1] != AT_REQUEST or message[2] != self.address:
+            self._skip_message()
+
+    def _check_crc(self, message):
+        crc = calculate_crc(message[:-2])
+        if crc != message[-2:]:
+            raise ValueError("CRC Mismatch")
+
+    def _skip_message(self, size):
+        try:
+            message = self.serial.read(size)
+        except:
+            pass
+
+    def _handle_message(self, message):
+        try:
+            self._check_crc(message)
+        except ValueError:
+            return AT_ERROR, [0,0,0,1]
+
+        if message[3] == SC_READ_REGISTER:
+            num_registers = message[4] + 1
+            start_register = int.from_bytes(message[5:7], 'big')
+            data = bytes()
+            for register in range(start_register, start_register + num_registers):
+                data += self.get_register_value(register)
+            return AT_RESPONSE, data
+
+    def get_register_value(self, register):
+        if register in self.registers:
+            return list(self.registers[register].to_bytes(4, 'big'))
+        else:
+            return list((0).to_bytes(4, 'big'))
+

sbus/crc.py

@@ -0,0 +1,55 @@
+import struct
+
+def calculate_crc(message):
+    """
+    Calculate the CRC on all bytes of the message
+    :return: The CRC value as a single int-16
+    """
+    crc = 0x0000
+    for char in message:
+        crc =  CRC16TABLE[((crc >> 8) ^ char) & 0xFF] ^ (crc << 8) & 0xFFFF
+    return struct.pack('>H', crc)
+
+CRC16TABLE = [0x0000, 0x1021, 0x2042, 0x3063, 0x4084, 0x50A5,
+              0x60C6, 0x70E7, 0x8108, 0x9129, 0xA14A, 0xB16B,
+              0xC18C, 0xD1AD, 0xE1CE, 0xF1EF, 0x1231, 0x0210,
+              0x3273, 0x2252, 0x52B5, 0x4294, 0x72F7, 0x62D6,
+              0x9339, 0x8318, 0xB37B, 0xA35A, 0xD3BD, 0xC39C,
+              0xF3FF, 0xE3DE, 0x2462, 0x3443, 0x0420, 0x1401,
+              0x64E6, 0x74C7, 0x44A4, 0x5485, 0xA56A, 0xB54B,
+              0x8528, 0x9509, 0xE5EE, 0xF5CF, 0xC5AC, 0xD58D,
+              0x3653, 0x2672, 0x1611, 0x0630, 0x76D7, 0x66F6,
+              0x5695, 0x46B4, 0xB75B, 0xA77A, 0x9719, 0x8738,
+              0xF7DF, 0xE7FE, 0xD79D, 0xC7BC, 0x48C4, 0x58E5,
+              0x6886, 0x78A7, 0x0840, 0x1861, 0x2802, 0x3823,
+              0xC9CC, 0xD9ED, 0xE98E, 0xF9AF, 0x8948, 0x9969,
+              0xA90A, 0xB92B, 0x5AF5, 0x4AD4, 0x7AB7, 0x6A96,
+              0x1A71, 0x0A50, 0x3A33, 0x2A12, 0xDBFD, 0xCBDC,
+              0xFBBF, 0xEB9E, 0x9B79, 0x8B58, 0xBB3B, 0xAB1A,
+              0x6CA6, 0x7C87, 0x4CE4, 0x5CC5, 0x2C22, 0x3C03,
+              0x0C60, 0x1C41, 0xEDAE, 0xFD8F, 0xCDEC, 0xDDCD,
+              0xAD2A, 0xBD0B, 0x8D68, 0x9D49, 0x7E97, 0x6EB6,
+              0x5ED5, 0x4EF4, 0x3E13, 0x2E32, 0x1E51, 0x0E70,
+              0xFF9F, 0xEFBE, 0xDFDD, 0xCFFC, 0xBF1B, 0xAF3A,
+              0x9F59, 0x8F78, 0x9188, 0x81A9, 0xB1CA, 0xA1EB,
+              0xD10C, 0xC12D, 0xF14E, 0xE16F, 0x1080, 0x00A1,
+              0x30C2, 0x20E3, 0x5004, 0x4025, 0x7046, 0x6067,
+              0x83B9, 0x9398, 0xA3FB, 0xB3DA, 0xC33D, 0xD31C,
+              0xE37F, 0xF35E, 0x02B1, 0x1290, 0x22F3, 0x32D2,
+              0x4235, 0x5214, 0x6277, 0x7256, 0xB5EA, 0xA5CB,
+              0x95A8, 0x8589, 0xF56E, 0xE54F, 0xD52C, 0xC50D,
+              0x34E2, 0x24C3, 0x14A0, 0x0481, 0x7466, 0x6447,
+              0x5424, 0x4405, 0xA7DB, 0xB7FA, 0x8799, 0x97B8,
+              0xE75F, 0xF77E, 0xC71D, 0xD73C, 0x26D3, 0x36F2,
+              0x0691, 0x16B0, 0x6657, 0x7676, 0x4615, 0x5634,
+              0xD94C, 0xC96D, 0xF90E, 0xE92F, 0x99C8, 0x89E9,
+              0xB98A, 0xA9AB, 0x5844, 0x4865, 0x7806, 0x6827,
+              0x18C0, 0x08E1, 0x3882, 0x28A3, 0xCB7D, 0xDB5C,
+              0xEB3F, 0xFB1E, 0x8BF9, 0x9BD8, 0xABBB, 0xBB9A,
+              0x4A75, 0x5A54, 0x6A37, 0x7A16, 0x0AF1, 0x1AD0,
+              0x2AB3, 0x3A92, 0xFD2E, 0xED0F, 0xDD6C, 0xCD4D,
+              0xBDAA, 0xAD8B, 0x9DE8, 0x8DC9, 0x7C26, 0x6C07,
+              0x5C64, 0x4C45, 0x3CA2, 0x2C83, 0x1CE0, 0x0CC1,
+              0xEF1F, 0xFF3E, 0xCF5D, 0xDF7C, 0xAF9B, 0xBFBA,
+              0x8FD9, 0x9FF8, 0x6E17, 0x7E36, 0x4E55, 0x5E74,
+              0x2E93, 0x3EB2, 0x0ED1, 0x1EF0]

tests/test_sbus.py

@@ -0,0 +1,5 @@
+from sbus import __version__
+
+
+def test_version():
+    assert __version__ == '0.1.0'