def spi(self):
spi = SPI(1, 0)
spi.mode = self.mode
spi.cshigh = False
spi.msh = 1000000
spi.bpw = 8
spi.lsbfirst = False
spi.open(1, 0)
# set cycle counts
spi.writebytes([0x04, 0x03, 0x20, 0x03, 0x20, 0x03,
0x20]) # 800 cycle counts
time.sleep(.01)
resolution = 3.3 # nT/LSB; corresponding to 800 cycle counts
# set sampling rate, in hertz
rate = 32
# display device settings
cycleX = spi.xfer2([0x84, 0x00, 0x00])
cycleY = spi.xfer2([0x86, 0x00, 0x00])
cycleZ = spi.xfer2([0x88, 0x00, 0x00])
sensor_settings1 = 'Cycle count [x, y, z]: [' + str(
int(hex(cycleX[1]) + hex(cycleX[2])[2:], 16)) + ', ' + str(
int(hex(cycleY[1]) + hex(cycleY[2])[2:], 16)) + ', ' + str(
int(hex(cycleZ[1]) + hex(cycleZ[2])[2:], 16)) + ']'
sensor_settings2 = 'Measurement rate: ' + str(rate) + ' Hz'
print(sensor_settings1)
print(sensor_settings2)
# list of timestamps for each measurement read
timestamp = []
# list to store raw data
raw = []
# set the total measuring time, in seconds
run_time = 30
print('Total measuring time: ' + str(run_time) + ' seconds')
t_end = time.time() + run_time
# main loop
trigger = time.time()
while time.time() < t_end:
timestamp.append(time.time())
target = (len(raw) + 1) * (1 / rate) + trigger
# initiate single measurement
spi.writebytes([0x00, 0x70])
condition = True
# loop to keep checking until measurement is completed
while condition:
# if DRDY is high (measurement is completed)
if format(spi.xfer2([0xB4, 0x00])[1], '#010b')[2] == '1':
# read measurement results
raw.append(
spi.xfer2([
0xA4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00
]))
condition = False
# if there is time remaining before next measurement
if time.time() < target:
# wait until appropriate time
time.sleep(target - time.time())
else:
print('Timing error.')
return
spi.close()
magX = []
magY = []
magZ = []
magn = []
for i in range(len(raw)):
results = []
for j in range(0, 9, 3):
data = float(
self.recast24to32(raw[i][j + 1], raw[i][j + 2],
raw[i][j + 3])) * resolution
status = float
results.append(data)
magX.append(results[0])
magY.append(results[1])
magZ.append(results[2])
magn.append(np.sqrt(results[0]**2 + results[1]**2 + results[2]**2))
start_time = timestamp[0]
time_diff = [0]
for k in range(len(timestamp)):
timestamp[k] = timestamp[k] - start_time
if k > 0:
time_diff.append(timestamp[k] - timestamp[k - 1])
mag_data = np.transpose(
np.array([magX, magY, magZ, magn, timestamp, time_diff]))
np.savetxt('mag_data_short_32Hz.txt',
mag_data,
header=sensor_settings1 + ' ; ' + sensor_settings2)
print('Successful measurement.')
return
def spi(self):
spi = SPI(1, 0)
spi.mode = self.mode
spi.cshigh = False
spi.msh = 1000000
spi.bpw = 8
spi.lsbfirst = False
spi.open(1, 0)
# set cycle counts
spi.writebytes([0x04, 0x03, 0xE8, 0x03, 0xE8, 0x03,
0xE8]) # 1000 cycle counts
time.sleep(.01)
# set continuous measurement mode
spi.writebytes([0x01, 0x79])
time.sleep(.01)
# set measurement rate
spi.writebytes([0x0B, 0x95])
time.sleep(.01)
resolution = 2.7 # nT/LSB; corresponding to 800 cycle counts
# display device settings
cycleX = spi.xfer2([0x84, 0x00, 0x00])
cycleY = spi.xfer2([0x86, 0x00, 0x00])
cycleZ = spi.xfer2([0x88, 0x00, 0x00])
sensor_settings1 = 'Cycle count [x, y, z]: [' + str(
int(hex(cycleX[1]) + hex(cycleX[2])[2:], 16)) + ', ' + str(
int(hex(cycleY[1]) + hex(cycleY[2])[2:], 16)) + ', ' + str(
int(hex(cycleZ[1]) + hex(cycleZ[2])[2:], 16)) + ']'
sensor_settings2 = 'Measurement rate: ' + hex(
spi.xfer2([0x8B, 0x00])[1])
print(sensor_settings1)
print(sensor_settings2)
# list of timestamps for each measurement read
timestamp = []
# list to check for rate errors: use this list to display an error if there are consecutive measurements where DRDY (status) is high.
error_check = []
# list to store the time values corresponding to each error
error_log = []
# list to store export data
mag_data = []
# set the total measuring time, in seconds
run_time = 10
print('Total measuring time: ' + str(run_time) + ' seconds')
t_end = time.time() + run_time
# Main loop
while time.time() < t_end:
# if the DRDY (status) pin is high
if format(spi.xfer2([0xB4, 0x00])[1], '#010b')[2] == '1':
# append appropriate values to lists
timestamp.append(time.time())
error_check.append(1)
# read measurement results
raw = spi.xfer2([
0xA4, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
])
results = []
for i in range(0, 9, 3):
data = float(
self.recast24to32(raw[i + 1], raw[i + 2],
raw[i + 3])) * resolution
status = float
results.append(data)
magXYZ = results
magn = np.sqrt(magXYZ[0]**2 + magXYZ[1]**2 + magXYZ[2]**2)
# if mag_data already contains some data
if len(mag_data) > 0:
# if DRDY was high two times in a row
if error_check[-2] == 1:
# store and display the error
error_log.append(timestamp[-1] - timestamp[0])
print('Error at t = ' + str(error_log[-1]) +
': Consecutive iterations with DRDY high.')
# append results to mag_data
mag_data = np.vstack(
(mag_data,
np.array([
magXYZ[0], magXYZ[1], magXYZ[2], magn,
timestamp[-1] - timestamp[0],
timestamp[-1] - timestamp[-2]
])))
# if mag_data contains nothing
else:
# create first line in mag_data
mag_data = np.array(
[magXYZ[0], magXYZ[1], magXYZ[2], magn, 0, 0])
# if the DRDY pin was NOT high
else:
# store appropriate value in error_check
error_check.append(0)
spi.close()
# if mag_data is empty, display error
if len(mag_data) == 0:
print('Error: DRDY never went high.')
return
# save data as txt file
np.savetxt('mag_data_short.txt',
mag_data,
header=sensor_settings1 + ' ; ' + sensor_settings2,
comments='')
# if there was a rate error -> save an additional txt file containing the corresponding time values
if len(error_log) > 0:
error_log = np.array(error_log)
np.savetxt(
'error_log_short.txt',
error_log,
header=
'Time values for which DRDY was high for consecutive measurements'
)
print('Successful measurement, with DRDY errors.')
return
print('Successful measurement.')
return