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from math import ceil
from . import Pmod
from . import MAILBOX_OFFSET
__author__ = "Cathal McCabe, Yun Rock Qu"
__copyright__ = "Copyright 2016, Xilinx"
__email__ = "pynq_support@xilinx.com"
PMOD_ALS_PROGRAM = "pmod_als.bin"
PMOD_ALS_LOG_START = MAILBOX_OFFSET+16
PMOD_ALS_LOG_END = PMOD_ALS_LOG_START+(1000*4)
RESET = 0x1
READ_SINGLE_VALUE = 0x3
READ_AND_LOG = 0x7
[docs]class Pmod_ALS(object):
"""This class controls a light sensor Pmod.
The Digilent Pmod ALS demonstrates light-to-digital sensing through a
single ambient light sensor. This is based on an ADC081S021
analog-to-digital converter and a TEMT6000X01 ambient light sensor.
Attributes
----------
microblaze : Pmod
Microblaze processor instance used by this module.
log_interval_ms : int
Time in milliseconds between sampled reads.
"""
def __init__(self, mb_info):
"""Return a new instance of an ALS object.
Parameters
----------
mb_info : dict
A dictionary storing Microblaze information, such as the
IP name and the reset name.
"""
self.microblaze = Pmod(mb_info, PMOD_ALS_PROGRAM)
self.log_interval_ms = 1000
[docs] def read(self):
"""Read current light value measured by the ALS Pmod.
Returns
-------
int
The current sensor value.
"""
self.microblaze.write_blocking_command(READ_SINGLE_VALUE)
data = self.microblaze.read_mailbox(0)
return data
[docs] def set_log_interval_ms(self, log_interval_ms):
"""Set the length of the log in the ALS Pmod.
This method can set the length of the log, so that users can read out
multiple values in a single log.
Parameters
----------
log_interval_ms : int
The length of the log in milliseconds, for debug only.
Returns
-------
None
"""
if log_interval_ms < 0:
raise ValueError("Log length should not be less than 0.")
self.log_interval_ms = log_interval_ms
self.microblaze.write_mailbox(0x4, log_interval_ms)
[docs] def start_log(self):
"""Start recording multiple values in a log.
This method will first call set_log_interval_ms() before sending the
command.
Returns
-------
None
"""
self.set_log_interval_ms(self.log_interval_ms)
self.microblaze.write_non_blocking_command(READ_AND_LOG)
[docs] def stop_log(self):
"""Stop recording multiple values in a log.
Simply send the command to stop the log.
Returns
-------
None
"""
self.microblaze.write_non_blocking_command(RESET)
[docs] def get_log(self):
"""Return list of logged samples.
Returns
-------
List of valid samples from the ALS sensor [0-255]
"""
# stop logging
self.stop_log()
# prep iterators and results list
[head_ptr, tail_ptr] = self.microblaze.read_mailbox(0x8, 2)
readings = []
# sweep circular buffer for samples
if head_ptr == tail_ptr:
return None
elif head_ptr < tail_ptr:
num_words = int(ceil((tail_ptr - head_ptr) / 4))
data = self.microblaze.read(head_ptr, num_words)
readings += data
else:
num_words = int(ceil((PMOD_ALS_LOG_END - head_ptr) / 4))
data = self.microblaze.read(head_ptr, num_words)
readings += data
num_words = int(ceil((tail_ptr - PMOD_ALS_LOG_START) / 4))
data = self.microblaze.read(PMOD_ALS_LOG_START, num_words)
readings += data
return readings