From f519abd7d70263a221289fa345ef2cd26b98451b Mon Sep 17 00:00:00 2001
From: Jake Read <jake.read@cba.mit.edu>
Date: Sat, 30 Dec 2023 02:09:49 -0500
Subject: [PATCH] prelim spi tests with mechanics intact
---
rpi_spi/code/spi_controller/pi_spi.py | 48 ++++++++++++++++++----
rpi_spi/code/spi_controller/plot_stamps.py | 43 +++++++++++++++++++
2 files changed, 83 insertions(+), 8 deletions(-)
create mode 100644 rpi_spi/code/spi_controller/plot_stamps.py
diff --git a/rpi_spi/code/spi_controller/pi_spi.py b/rpi_spi/code/spi_controller/pi_spi.py
index 78ec483..6c2c166 100644
--- a/rpi_spi/code/spi_controller/pi_spi.py
+++ b/rpi_spi/code/spi_controller/pi_spi.py
@@ -1,22 +1,54 @@
-import spidev
+import spidev, time
+# import numpy as np
+# from plot_stamps import plot_stamps
-bitrate = 1000000
+bitrate = 10000000
print(f'rate {bitrate/1e6}MBit/s bit period should be {1000000000/bitrate}ns')
spi = spidev.SpiDev()
spi.open(0, 0)
spi.max_speed_hz = bitrate
-spi.mode = 0b00
+spi.mode = 0b10
-test_pck = bytearray(32)
+pck_len = 64
+stamp_count = 10000
+# stamps = np.zeros(stamp_count)
+
+test_pck = bytearray(pck_len)
for b in range(len(test_pck)):
- test_pck[b] = b
+ test_pck[b] = b + 1
print(test_pck)
-for i in range(1000):
+# TODO will be to finish making these plots,
+# need to install pandas and numpy here w a venv
+# for now I'm just going to turn the rate up until things go wrong
+bonked = False
+for i in range(stamp_count):
+ if bonked:
+ break
ret = spi.xfer(test_pck)
- print(ret)
+ # stamps[i] = time.perf_counter() * 1e6
+ start = -1
+ for j in range(len(ret)):
+ if start == -1:
+ if ret[j] == 0:
+ start = j
+ continue
+ else:
+ if ret[j] != j - start:
+ print(f'BONK at {i} char {j} {start} {ret[j]}')
+ print(ret)
+ bonked = True
+ break
+
+spi.close()
+
+# plot_stamps(stamps, stamp_count, pck_len)
-spi.close()
\ No newline at end of file
+# 1Mbit seems solid,
+# 2.5Mbit and we have very occasional starvation
+# 5Mbit and we have at least one bad packet every run (1/1000?)
+# 5Mbit with more F_CPU (250MHz) it is obviously improved (1/5000?)
+# 10Mbit at 250MHz we are back to ~ (1/2000) starvations,
\ No newline at end of file
diff --git a/rpi_spi/code/spi_controller/plot_stamps.py b/rpi_spi/code/spi_controller/plot_stamps.py
new file mode 100644
index 0000000..805d3d0
--- /dev/null
+++ b/rpi_spi/code/spi_controller/plot_stamps.py
@@ -0,0 +1,43 @@
+import pandas as pd
+import matplotlib.pyplot as plt
+
+def plot_stamps(stamps, stamp_count, pck_len):
+ # make df from stamps
+ df = pd.DataFrame({'timestamps': stamps})
+
+ # calculate deltas between stamps
+ df['deltas'] = df['timestamps'].diff()
+
+ # clean NaN's
+ df = df.dropna()
+
+ # wipe obviously-wrong deltas (i.e. the 1st, which goes 0-start-us)
+ df = df[df['deltas'] < 10000]
+
+ # Plotting
+ fig, ax1 = plt.subplots(figsize=(11, 3))
+
+ ax1.set_xlim([50, 2000])
+
+ # Primary x-axis (time deltas)
+ df['deltas'].plot(kind='hist', bins=50, ax=ax1)
+ ax1.set_xlabel('Time-Stamp Deltas (us) and equivalent (MBits/s)')
+ ax1.set_ylabel(f'Frequency (of {stamp_count})')
+
+ # get axis ticks to calculate equivalent bandwidths
+ x_ticks = ax1.get_xticks()
+ ax1.set_xticks(x_ticks)
+ bandwidths = [((pck_len * 8) * (1e6 / x)) / 1e6 for x in x_ticks]
+ ticks = []
+
+ for i in range(len(x_ticks)):
+ print(i, x_ticks[i], bandwidths[i])
+ ticks.append(f"{x_ticks[i]:.0f} ({bandwidths[i]:.3f})")
+
+ ax1.set_xticklabels(ticks)
+
+ plt.title(f'Single-Source COBS Data Sink Deltas, pck_len={pck_len}')
+
+ plt.tight_layout()
+
+ plt.show()
\ No newline at end of file
--
GitLab