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272 | class SCServo:
def __init__(self, driver: SCServoDriver, id: int, endian: str = "big"):
self.driver = driver
self.id = id
self.endian = endian
async def _read(self, address: int, length: int) -> tuple[bytes | None, int]:
pkt = Packet(self.id, Instruction.READ, [address, length])
resp = await self.driver.send_packet(pkt)
if resp:
# We return data if length matches, even if error is set
# because some errors (like overload) might not prevent reading data
if len(resp.params) == length:
return bytes(resp.params), resp.instruction
elif resp.instruction != 0:
# If error set and no data (or mismatch), return None data but error code
return None, resp.instruction
return None, -1
async def _write(self, address: int, data: list[int]) -> int:
params = [address] + data
pkt = Packet(self.id, Instruction.WRITE, params)
resp = await self.driver.send_packet(pkt)
if resp:
return resp.instruction
return -1
async def _reg_write(self, address: int, data: list[int]) -> int:
params = [address] + data
pkt = Packet(self.id, Instruction.REG_WRITE, params)
resp = await self.driver.send_packet(pkt)
if resp:
return resp.instruction
return -1
async def action(self) -> int:
pkt = Packet(self.id, Instruction.ACTION, [])
# If specific ID, it returns status packet.
resp = await self.driver.send_packet(pkt)
if resp:
return resp.instruction
return -1
async def ping(self) -> int:
pkt = Packet(self.id, Instruction.PING, [])
resp = await self.driver.send_packet(pkt)
if resp:
return resp.instruction
return -1
async def enable_torque(self, enable: bool = True) -> int:
val = TorqueEnable.ON if enable else TorqueEnable.OFF
return await self._write(Memory.TORQUE_ENABLE, [val])
def _split_word(self, val: int) -> list[int]:
val = val & 0xFFFF
if self.endian == "big":
return [(val >> 8) & 0xFF, val & 0xFF]
return [val & 0xFF, (val >> 8) & 0xFF]
async def set_position(self, position: int, time: int = 0, speed: int = 0) -> int:
# For SC Series (Big Endian):
# Write to GOAL_POSITION_L (42)
# Order: PosH, PosL, TimeH, TimeL, SpeedH, SpeedL
# Position is simply raw value (no sign conversion needed usually for write in SC protocol)
data = []
data.extend(self._split_word(position))
data.extend(self._split_word(time))
data.extend(self._split_word(speed))
return await self._write(Memory.GOAL_POSITION_L, data)
async def reg_write_position(self, position: int, time: int = 0, speed: int = 0) -> int:
data = []
data.extend(self._split_word(position))
data.extend(self._split_word(time))
data.extend(self._split_word(speed))
return await self._reg_write(Memory.GOAL_POSITION_L, data)
async def read_position(self) -> int | None:
data, _ = await self._read(Memory.PRESENT_POSITION_L, 2)
if data:
raw = make_word(data[0], data[1])
return from_sign_magnitude(raw, 15)
return None
async def read_speed(self) -> int | None:
data, current_error = await self._read(Memory.PRESENT_SPEED_L, 2)
if data:
raw = make_word(data[0], data[1])
return from_sign_magnitude(raw, 15)
return None
async def read_load(self) -> int | None:
data, _ = await self._read(Memory.PRESENT_LOAD_L, 2)
if data:
raw = make_word(data[0], data[1])
return from_sign_magnitude(raw, 10)
return None
async def read_voltage(self) -> int | None:
# Voltage is 1 byte, unit 0.1V
data, _ = await self._read(Memory.PRESENT_VOLTAGE, 1)
if data:
return data[0]
return None
async def read_temperature(self) -> int | None:
data, _ = await self._read(Memory.PRESENT_TEMPERATURE, 1)
if data:
return data[0]
return None
async def read_status(self) -> dict:
# Split reads to avoid reading gaps (undefined registers) which might return garbage or cause offsets
# Block 1: 56-63 (Pos, Speed, Load, Volt, Temp)
data_main, error_main = await self._read(Memory.PRESENT_POSITION_L, 8)
# Block 2: 66 (Moving)
data_moving, error_moving = await self._read(Memory.MOVING, 1)
# Block 3: 69-70 (Current)
data_current, error_current = await self._read(Memory.PRESENT_CURRENT_L, 2)
result = {}
# Union of errors (prioritize main)
if error_main != -1:
result["error"] = error_main
elif error_moving != -1:
result["error"] = error_moving
elif error_current != -1:
result["error"] = error_current
if data_main and len(data_main) == 8:
raw_pos = make_word(data_main[0], data_main[1], self.endian)
raw_speed = make_word(data_main[2], data_main[3], self.endian)
raw_load = make_word(data_main[4], data_main[5], self.endian)
volt = data_main[6]
temp = data_main[7]
result.update(
{
"position": raw_pos,
"speed": from_sign_magnitude(raw_speed, 15),
"speed_raw": raw_speed,
"load": from_sign_magnitude(raw_load, 10),
"voltage": volt,
"temperature": temp,
}
)
if data_moving:
result["moving"] = data_moving[0]
if data_current and len(data_current) == 2:
raw_current = make_word(data_current[0], data_current[1], self.endian)
result["current"] = from_sign_magnitude(raw_current, 15)
return result
async def set_id(self, new_id: int) -> bool:
"""
Change the ID of the servo.
Note: This changes EPROM. Requires Unlock.
"""
# Unlock EPROM
await self._write(Memory.LOCK, [0])
# Write new ID
res = await self._write(Memory.ID, [new_id])
# Lock EPROM
await self._write(Memory.LOCK, [1])
return res == 0 # or success check
async def wait_for_stop(
self,
interval: float = 0.05,
timeout: float = 5.0,
blocked_threshold: int = 5,
load_threshold: int = 100,
) -> str:
"""
Wait until the servo stops moving.
Returns reason: "reached", "blocked", "timeout"
blocked_threshold: Minimal position change per second to consider moving.
If moving bit is set but position changes less than this, valid as blocked.
HOWEVER, simple approach: check if position changes.
load_threshold: If load is above this value when stopping, consider it blocked.
"""
import time
# Give a small delay for the servo to update its Moving bit after a write command
await asyncio.sleep(0.1)
start_time = time.time()
last_pos = -1
blocked_counter = 0
while (time.time() - start_time) < timeout:
status = await self.read_status()
if not status:
await asyncio.sleep(interval)
continue
moving = status.get("moving", 1) # Default to 1 (moving) if key missing
current_pos = status.get("position", 0)
current_load = status.get("load", 0)
# If moving flag goes to 0, we stopped.
# But did we reach target or hit an obstacle?
if moving == 0:
# If load is significant (e.g. > 50 or < -50), it means we are forcing against something
# Or if error bit is set (like overload, though that's in error byte)
if abs(current_load) > load_threshold:
logger.warning(f"Blocked: Stopped but high load ({current_load} > {load_threshold})")
return "blocked"
return "reached"
# Check for blocking while moving=1 (stalled but trying)
# If position hasn't changed significantly for X steps while Moving is 1
if abs(current_pos - last_pos) < blocked_threshold:
blocked_counter += 1
else:
blocked_counter = 0
last_pos = current_pos
# If we haven't moved enough for N cycles (defines blocking sensitivity)
# interval 0.05 * 10 = 0.5 sec
if blocked_counter > 10:
logger.warning(f"Blocked: Stalled at {current_pos} (stuck for 0.5s)")
return "blocked"
await asyncio.sleep(interval)
return "timeout"
|