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72 lines
1.9 KiB
Python
72 lines
1.9 KiB
Python
# Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http:#www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Internal use only.
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This file provide method to control programmable attenuator.
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"""
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import time
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import serial
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import codecs
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def set_att(port, att, att_fix=False):
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"""
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set attenuation value on the attenuator
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:param port: serial port for attenuator
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:param att: attenuation value we want to set
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:param att_fix: fix the deviation with experience value
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:return: True or False
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"""
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assert 0 <= att <= 62
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# fix att
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if att_fix:
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if att >= 33 and (att - 30 + 1) % 4 == 0:
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att_t = att - 1
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elif att >= 33 and (att - 30) % 4 == 0:
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att_t = att + 1
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else:
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att_t = att
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else:
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att_t = att
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serial_port = serial.Serial(port, baudrate=9600, rtscts=False, timeout=0.1)
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if serial_port.isOpen() is False:
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raise IOError("attenuator control, failed to open att port")
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cmd_hex = "7e7e10{:02x}{:x}".format(att_t, 0x10 + att_t)
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exp_res_hex = "7e7e20{:02x}00{:x}".format(att_t, 0x20 + att_t)
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cmd = codecs.decode(cmd_hex, "hex")
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exp_res = codecs.decode(exp_res_hex, "hex")
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serial_port.write(cmd)
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res = b""
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for i in range(5):
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res += serial_port.read(20)
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if res == exp_res:
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result = True
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break
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time.sleep(0.1)
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else:
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result = False
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serial_port.close()
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return result
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