Select Git revision
-
Neil Gershenfeld authoredNeil Gershenfeld authored
pi_spi.py 1.25 KiB
import spidev, time
import numpy as np
from plot_stamps import plot_stamps
bitrate = 11000000
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 = 0b10
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 + 1
print(test_pck)
bonked = False
bonk_count = 0
for i in range(stamp_count):
# if bonked:
# break
ret = spi.xfer(test_pck)
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)
bonk_count += 1
bonked = True
break
spi.close()
print(f"bonk {bonk_count} / {stamp_count}")
plot_stamps(stamps, stamp_count, pck_len, bonk_count / stamp_count)
# 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,