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Vision latency #62

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Vision latency #62

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9f4cdc7
Reduce network load by only pinging RasPi every 0.5s
james-ward Mar 6, 2019
9d5a022
Calculate exponential smoothing in a more intuitive fashion
james-ward Mar 6, 2019
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7 changes: 5 additions & 2 deletions components/vision.py
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Original file line number Diff line number Diff line change
Expand Up @@ -90,13 +90,16 @@ def _get_pose_delta(self, t):

def ping(self):
"""Send a ping to the RasPi to determine the connection latency."""
self.ping_time = time.monotonic()
t = time.monotonic()
if t - self.ping_time > 0.5:
# Only ping every 500ms - don't keep smashing NetworkTables
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Given that we're still constantly flushing NetworkTables here, the impact this will have on traffic is negligible.

The performance impact should also be close-to-negligible iff we have the latest wpilib.

self.ping_time = time.monotonic()

def pong(self):
"""Receive a pong from the RasPi to determine the connection latency."""
if abs(self.rio_pong_time - self.last_pong) > 1e-4: # Floating point comparison
alpha = 0.0 # Exponential averaging
self.latency = alpha * self.latency + (1 - alpha) * (
self.latency = (1 - alpha) * self.latency + alpha * (
self.rio_pong_time - self.raspi_pong_time
)
self.last_pong = self.rio_pong_time