def _open_led_i2c():
"""Open the i2c port on the VEC USB for led controller operations."""
# Construct string to set channel number to 3
channel_str = PCA9546_WRITE_ADDRESS + '\x08'
# Port A I2C for PCA9546A
vec = MPSSE()
vec.Open(0x0403, 0x6011, I2C, ONE_HUNDRED_KHZ, MSB, IFACE_A)
# Port B I2C for debug leds (don't need the io expander for the LED Port)
gpio = MPSSE()
gpio.Open(0x0403, 0x6011, I2C, ONE_HUNDRED_KHZ, MSB, IFACE_B)
# Set RESET line on PCA9546A to high to activate switch
vec.PinHigh(GPIOL0)
# Set channel on PCA9546A to 3 for PCA9632 (LED Port) Keep in mind this
# also is connected to the MAX11608
vec.Start()
vec.Write(channel_str)
vec.Stop()
# verify channel was set.
vec.Start()
vec.Write(PCA9546_READ_ADDRESS)
vec.SendNacks()
reg = vec.Read(1)
vec.Stop()
reg = ord(reg)
if reg != 0x08:
raise ValueError('Failed to set PCA9546A Control Register to 0x08. Is 0x{:02x}'.format(reg))
vec.SendAcks()
vec.Start()
# Configure PCA9632 for our setup (IE totem pole with inverted driver output, etc)
# Writes to Mode 1 and Mode 2 Registers
vec.Start()
vec.Write('\xC4\x80\x00\x35')
vec.Stop()
return vec, gpio
def configure_differential_pressure(channel):
""" Configure the differential pressure sensor for 9 bit resolution.
Default is 12. This needs to be done once per power up. For our case we call this
on synse container startup.
Args:
channel: The channel to configure.
"""
logger.debug(
'Configuring Differential Pressure sensor on channel {}'.format(
channel))
# Port A I2C for PCA9546A
vec = MPSSE()
vec.Open(0x0403, 0x6011, I2C, ONE_HUNDRED_KHZ, MSB, IFACE_A)
# Set RESET line on PCA9546A to high to activate switch
vec.PinHigh(GPIOL0)
time.sleep(0.001)
channel_str = PCA9546_WRITE_ADDRESS + chr(channel)
logger.debug('PCA9546_WRITE_ADDRESS is: {}'.format(
hexlify(PCA9546_WRITE_ADDRESS)))
logger.debug('channel_str is: {}'.format(hexlify(channel_str)))
vec.Start()
vec.Write(channel_str)
vec.Stop()
logger.debug('PCA9546_READ_ADDRESS is: {}'.format(
hexlify(PCA9546_READ_ADDRESS)))
# verify channel was set
vec.Start()
vec.Write(PCA9546_READ_ADDRESS)
vec.SendNacks()
reg = vec.Read(1)
vec.Stop()
vec.SendAcks()
logger.debug('PCA9546A Control Register: 0x{:02x}'.format(ord(reg)))
# Configure Sensor
# In the application note for changing measurement resolution three things must be met.
# 1. Read the advanced user register.
# 2. Define the new register entry according to the desired resolution.
# 3. Write the new value to the advanced register.
vec.Start()
vec.Write('\x80\xE5')
vec.Start()
vec.Write('\x81')
# At this point the sensor needs to hold the master but the FT4232 doesn't do clock stretching.
time.sleep(0.001) # This stays at 1 ms regardless of sensor resolution.
# Read the three bytes out of the DPS sensor (two data bytes and crc)
sensor_data = vec.Read(3)
logger.debug('Raw sensor_data: {}'.format(hexlify(sensor_data)))
vec.Stop()
# write new value for 9 bit resolution (0b000 for bits 9 - 11)
if _crc8(sensor_data):
# Hardcoded 9 bit sensor resolution.
sensor_int = 0x7182
msb = sensor_int >> 8
lsb = sensor_int & 0xFF
register_str = '\x80\xE4' + chr(msb) + chr(lsb)
vec.Start()
vec.Write(register_str)
vec.Stop()
logger.debug(
'Configured DP Sensor on channel {} for 9 bit resolution.'.format(
channel))
rc = 0
else:
logger.error('CRC failed configuring DP Sensor.')
rc = 1
vec.Stop()
vec.Close()
return rc