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from struct import pack
from struct import unpack
from math import ceil
from . import Pmod
from . import MAILBOX_OFFSET
__author__ = "Thomas Fors"
__copyright__ = "Copyright 2016, Xilinx"
__email__ = "pynq_support@xilinx.com"
PMOD_TC1_PROGRAM = "pmod_tc1.bin"
PMOD_TC1_LOG_START = MAILBOX_OFFSET+16
PMOD_TC1_LOG_END = PMOD_TC1_LOG_START+(1000*4)
RESET = 0x1
READ_SINGLE_VALUE = 0x3
READ_AND_LOG = 0x7
[docs]def reg_to_tc(reg_val):
"""Extracts Thermocouple temperature from 32-bit register value.
Parameters
----------
reg_val : int
32-bit TC1 register value
Returns
-------
float
The thermocouple temperature in degC.
"""
v = reg_val >> 18
if v & 0x00020000:
v |= 0xfffc0000
else:
v &= 0x0003ffff
v = unpack('<i', pack('<I', v))[0]
return v * 0.25
[docs]def reg_to_ref(reg_val):
"""Extracts Ref Junction temperature from 32-bit register value.
Parameters
----------
reg_val : int
32-bit TC1 register value
Returns
-------
float
The reference junction temperature in degC.
"""
v = reg_val >> 4
if v & 0x00000800:
v |= 0xfffff000
else:
v &= 0x00000fff
v = unpack('<i', pack('<I', v))[0]
return v * 0.0625
[docs]def reg_to_alarms(reg_val):
"""Extracts Alarm flags from 32-bit register value.
Parameters
----------
reg_val : int
32-bit TC1 register value
Returns
-------
u32
The alarm flags from the TC1.
bit 0 = 1 if thermocouple connection is open-circuit;
bit 1 = 1 if thermocouple connection is shorted to generated;
bit 2 = 1 if thermocouple connection is shorted to VCC;
bit 16 = 1 if any if bits 0-2 are 1.
"""
return reg_val & 0x0001000f
[docs]class Pmod_TC1(object):
"""This class controls a thermocouple Pmod.
The Digilent PmodTC1 is a cold-junction thermocouple-to-digital converter
module designed for a classic K-Type thermocouple wire. With Maxim
Integrated's MAX31855, this module reports the measured temperature in
14-bits with 0.25 degC resolution.
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 a TC1 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_TC1_PROGRAM)
self.log_interval_ms = 1000
[docs] def read_raw(self):
"""Read full 32-bit register of TC1 Pmod.
Returns
-------
int
The current register contents.
"""
self.microblaze.write_blocking_command(READ_SINGLE_VALUE)
return self.microblaze.read_mailbox(0)
[docs] def read_junction_temperature(self):
"""Read the reference junction temperature.
Returns
-------
float
The reference junction temperature in degC.
"""
return reg_to_ref(self.read_raw())
[docs] def read_thermocouple_temperature(self):
"""Read the reference junction temperature.
Returns
-------
float
The thermocouple temperature in degC.
"""
return reg_to_tc(self.read_raw())
[docs] def read_alarm_flags(self):
"""Read the alarm flags from the raw value.
Returns
-------
u32
The alarm flags from the TC1.
bit 0 = 1 if thermocouple connection is open-circuit;
bit 1 = 1 if thermocouple connection is shorted to generated;
bit 2 = 1 if thermocouple connection is shorted to VCC;
bit 16 = 1 if any if bits 0-2 are 1.
"""
return reg_to_alarms(self.read_raw())
[docs] def set_log_interval_ms(self, log_interval_ms):
"""Set the length of the log in the TC1 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 writting to
the MMIO.
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 write to the MMIO to stop the log.
Returns
-------
None
"""
self.microblaze.write_non_blocking_command(RESET)
[docs] def get_log(self):
"""Return list of logged samples.
Note
----
The logged samples are raw 32-bit samples captured from the sensor.
Returns
-------
list
List of valid samples from the TC1 sensor
"""
# 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_TC1_LOG_END - head_ptr) / 4))
data = self.microblaze.read(head_ptr, num_words)
readings += data
num_words = int(ceil((tail_ptr - PMOD_TC1_LOG_START) / 4))
data = self.microblaze.read(PMOD_TC1_LOG_START, num_words)
readings += data
return readings