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work in progress MKS 901P vacuum transducer sensor library and command-line program.
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| """ | |
| usage: mks_901p.py [-h] [--find_baud] [--baud BAUD] [-unit] serial_port | |
| positional arguments: | |
| serial_port the Windows COM port or path to a linux serial port | |
| optional arguments: | |
| -h, --help show this help message and exit | |
| --find_baud tries to access the sensor over all supported baud rates, | |
| prints which is successful | |
| --baud BAUD baud rate to connect with, defaults to 9600 (901p factory | |
| default) | |
| -unit print pressure unit with each reading | |
| """ | |
| # xxx = Transducer communication address (001 to 253. Broadcast addresses: 254, 255) | |
| baud_supported = [4800, 9600, 19200, 38400, 57600, 115200, 230400] | |
| commands = { | |
| 'Communication information': { | |
| 'get_baud_rate': { | |
| 'Command': '@{}BR?;FF', | |
| 'Response': '@xxxACK9600;FF', | |
| 'Explanation': 'Communication baud rate (4800, 9600, 19200, 38400, 57600, 115200,230400)' | |
| }, | |
| 'get_address': { | |
| 'Command': '@{}AD?;FF', | |
| 'Response': '@xxxACK253;FF', | |
| 'Explanation': 'Transducer communication address (001 to 253)' | |
| }, | |
| 'get_comms_delay': { | |
| 'Command': '@{}RSD?;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanation': 'Communication delay between receive and transmit sequence.' | |
| } | |
| }, | |
| 'Pressure reading': { | |
| 'pirani': { | |
| 'Command': '@{}PR1?;FF', | |
| 'Response': '@xxxACK1.23E-3;FF', | |
| 'Explanation': 'MicroPirani sensor pressure as 3 digit floating point value.'}, | |
| 'piezo': { | |
| 'Command': '@{}PR2?;FF', | |
| 'Response': '@xxxACK-7.60E+2;FF', | |
| 'Explanation': 'Piezo differential sensor pressure as 3 digit floating point value.'}, | |
| 'combined_3_digit': { | |
| 'Command': '@{}PR3?;FF', | |
| 'Response': '@xxxACK1.23E-3;FF', | |
| 'Explanation': 'Combined reading as 3 digit floating point value.'}, | |
| 'combined_4_digit': { | |
| 'Command': '@{}PR4?;FF', | |
| 'Response': '@xxxACK1.234E-3;FF', | |
| 'Explanation': 'Combined reading as 4 digit floating point value.'} | |
| }, | |
| 'Setpoint information': { | |
| 'get_setpoint_1_status': { | |
| 'Command': '@{}SS1?;FF', | |
| 'Response': '@xxxACKSET;FF', | |
| 'Explanation': 'Set point relay 1-3 status (SET=Relay energized / CLEAR=Relay deenergized'}, | |
| 'get_setpoint_2_status': { | |
| 'Command': '@{}SS2?;FF', | |
| 'Response': '@xxxACKSET;FF', | |
| 'Explanation': 'Set point relay 1-3 status (SET=Relay energized / CLEAR=Relay deenergized'}, | |
| 'get_setpoint_3_status': { | |
| 'Command': '@{}SS3?;FF', | |
| 'Response': '@xxxACKSET;FF', | |
| 'Explanation': 'Set point relay 1-3 status (SET=Relay energized / CLEAR=Relay deenergized'}, | |
| 'get_setpoint_1': { | |
| 'Command': '@{}SP1?;FF', | |
| 'Response': '@xxxACK1.00E-2;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'get_setpoint_2': { | |
| 'Command': '@{}SP2?;FF', | |
| 'Response': '@xxxACK1.00E-2;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'get_setpoint_3': { | |
| 'Command': '@{}SP3?;FF', | |
| 'Response': '@xxxACK1.00E-2;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'get_hysteresis_1': { | |
| 'Command': '@{}SH1?;FF', | |
| 'Response': '@xxxACK1.10E-2;FF', | |
| 'Explanation': 'Set point 1-3 hystereses switch value.'}, | |
| 'get_hysteresis_2': { | |
| 'Command': '@{}SH2?;FF', | |
| 'Response': '@xxxACK1.10E-2;FF', | |
| 'Explanation': 'Set point 1-3 hystereses switch value.'}, | |
| 'get_hysteresis_3': { | |
| 'Command': '@{}SH3?;FF', | |
| 'Response': '@xxxACK1.10E-2;FF', | |
| 'Explanation': 'Set point 1-3 hystereses switch value.'}, | |
| 'get_setpoint_1_enabled': { | |
| 'Command': '@{}EN1?;FF', | |
| 'Response': '@xxxACKDIFF;FF', | |
| 'Explanation': 'Set point 1-3 enable status ( OFF, DIFF=Piezo differential or ABS=Absolute Piezo)'}, | |
| 'get_setpoint_2_enabled': { | |
| 'Command': '@{}EN2?;FF', | |
| 'Response': '@xxxACKDIFF;FF', | |
| 'Explanation': 'Set point 1-3 enable status ( OFF, DIFF=Piezo differential or ABS=Absolute Piezo)'}, | |
| 'get_setpoint_3_enabled': { | |
| 'Command': '@{}EN3?;FF', | |
| 'Response': '@xxxACKDIFF;FF', | |
| 'Explanation': 'Set point 1-3 enable status ( OFF, DIFF=Piezo differential or ABS=Absolute Piezo)'}, | |
| 'get_setpoint1_relay_direction': { | |
| 'Command': '@{}SD1?;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW) If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'get_setpoint2_relay_direction': { | |
| 'Command': '@{}SD2?;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW) If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'get_setpoint3_relay_direction': { | |
| 'Command': '@{}SD3?;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW) If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'get_setpoint_safety_delay': { | |
| 'Command': '@{}SPD?;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanation': 'Setpoint safety delay'} | |
| }, | |
| 'Transducer information': { | |
| 'get_model': { | |
| 'Command': '@{}MD?;FF', | |
| 'Response': '@xxxACK901P;FF', | |
| 'Explanation': 'Model number (901P)'}, | |
| 'get_devicetype': { | |
| 'Command': '@{}DT?;FF', | |
| 'Response': '@xxxACKLoadlock;FF', | |
| 'Explanation': 'Device type name (MicroPirani)'}, | |
| 'get_mfg': { | |
| 'Command': '@{}MF?;FF', | |
| 'Response': '@xxxACKMKS;FF', | |
| 'Explanation': 'Manufacturer name (MKS)'}, | |
| 'get_hw_version': { | |
| 'Command': '@{}HV?;FF', | |
| 'Response': '@xxxACKA;FF', | |
| 'Explanation': 'Hardware version'}, | |
| 'get_fw_version': { | |
| 'Command': '@{}FV?;FF', | |
| 'Response': '@xxxACK1.00;FF', | |
| 'Explanation': 'Firmware version'}, | |
| 'get_serial_num': { | |
| 'Command': '@{}SN?;FF', | |
| 'Response': '@xxxACK08350123456;FF', | |
| 'Explanation': 'Serial number'}, | |
| 'get_switch': { | |
| 'Command': '@{}SW?;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanation': 'Switch enable'}, | |
| 'get_time_on': { | |
| 'Command': '@{}TIM?;FF', | |
| 'Response': '@xxxACK12345;FF', | |
| 'Explanation': 'Time on (hours of operation )'}, | |
| 'get_pirani_temp': { | |
| 'Command': '@{}TEM?;FF', | |
| 'Response': '@xxxACK2.50E+1;FF', | |
| 'Explanation': 'MicroPirani sensor temperature'}, | |
| 'get_usertext': { | |
| 'Command': '@{}UT?;FF', | |
| 'Response': '@xxxACKVACUUM1;FF', | |
| 'Explanation': 'User programmed text string'}, | |
| 'get_status': { | |
| 'Command': '@{}T?;FF', | |
| 'Response': '@xxxACKO;FF', | |
| 'Explanation': 'Transducer status check'} | |
| }, | |
| 'Calibration and adjustment information': { | |
| 'get_pressure_unit': { | |
| 'Command': '@{}U?;FF', | |
| 'Response': '@xxxACKTORR;FF', | |
| 'Explanation': 'Pressure unit setup (Torr, mbar or Pascal)'}, | |
| 'get_calibration_gas': { | |
| 'Command': '@{}GT?;FF', | |
| 'Response': '@xxxACKNITROGEN;FF', | |
| 'Explanation': 'MicroPirani sensor calibration gas (Nitrogen, Air, Argon, Helium, Hydrogen, H2O, Neon, CO2, Xenon)'}, | |
| 'get_factory_diff_zero_point': { | |
| 'Command': '@{}VAC?;FF', | |
| 'Response': '@xxxACK5.12E-5;FF', | |
| 'Explanation': 'Provides delta pressure value between current vacuum zero adjustment and factory calibration.'}, | |
| 'get_factory_diff_atmosphere': { | |
| 'Command': '@{}ATM?;FF', | |
| 'Response': '@xxxACK1.22E+1;FF', | |
| 'Explanation': 'Provides delta pressure value between current atmospheric adjustment and factory calibration.'}, | |
| 'get_analog_out_1': { | |
| 'Command': '@{}AO1?;FF', | |
| 'Response': '@xxxACK10;FF', | |
| 'Explanation': 'Analog voltage output 1: Pressure assignment and calibration. (first digit is pressure assignment, second and third digit is calibration)'}, | |
| 'get_analog_out_2': { | |
| 'Command': '@{}AO2?;FF', | |
| 'Response': '@xxxACK10;FF', | |
| 'Explanation': 'Analog voltage output 2: Pressure assignment and calibration. (first digit is pressure assignment, second and third digit is calibration)'} | |
| }, | |
| 'Setpoint setup and configuration': { | |
| 'set_setpoint_1':{ | |
| 'Command': '@{}SP1!2.00E+1;FF', | |
| 'Response': '@xxxACK2.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'set_setpoint_2':{ | |
| 'Command': '@{}SP2!2.00E+1;FF', | |
| 'Response': '@xxxACK2.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'set_setpoint_3':{ | |
| 'Command': '@{}SP3!2.00E+1;FF', | |
| 'Response': '@xxxACK2.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 switch value.'}, | |
| 'set_hysteresis_1':{ | |
| 'Command': '@{}SH1!5.00E+1;FF', | |
| 'Response': '@xxxACK5.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 hysteresis switch value.'}, | |
| 'set_hysteresis_2':{ | |
| 'Command': '@{}SH2!5.00E+1;FF', | |
| 'Response': '@xxxACK5.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 hysteresis switch value.'}, | |
| 'set_hysteresis_3':{ | |
| 'Command': '@{}SH3!5.00E+1;FF', | |
| 'Response': '@xxxACK5.00E+1;FF', | |
| 'Explanation': 'Set point 1-3 hysteresis switch value.'}, | |
| 'enable_setpoint_1':{ | |
| 'Command': '@{}EN1!ON;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanantion': 'Set point 1-3 enable status (ON or OFF)'}, | |
| 'enable_setpoint_2':{ | |
| 'Command': '@{}EN2!ON;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanantion': 'Set point 1-3 enable status (ON or OFF)'}, | |
| 'enable_setpoint_3':{ | |
| 'Command': '@{}EN3!ON;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanantion': 'Set point 1-3 enable status (ON or OFF)'}, | |
| 'set_setpoint1_relay_direction':{ | |
| 'Command': '@{}SD1!BELOW;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW). If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'set_setpoint2_relay_direction':{ | |
| 'Command': '@{}SD2!BELOW;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW). If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'set_setpoint3_relay_direction':{ | |
| 'Command': '@{}SD3!BELOW;FF', | |
| 'Response': '@xxxACKBELOW;FF', | |
| 'Explanation': 'Set point relay direction (ABOVE or BELOW). If set to above relay will be energized above setpoint value. If set to below relay will be energized below setpoint value.'}, | |
| 'set_setpoint_safety_delay':{ | |
| 'Command': '@{}SPD!ON;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanation': 'Setpoint safety delay (prevent pulse trig of setpoint)'} | |
| }, | |
| 'Communication setup': { | |
| 'set_baud_rate': { | |
| 'Command': '@{}BR!19200;FF', | |
| 'Response': '@xxxACK19200;FF', | |
| 'Explanation': 'Set communication Baud rate (4800, 9600, 19200, 38400, 57600, 115200, 230400)'}, | |
| 'set_address': { | |
| 'Command': '@{}AD!123;FF', | |
| 'Response': '@xxxACK123;FF', | |
| 'Explanation': 'Set Transducer communication address (001 to 253)'}, | |
| 'set_comms_delay': { | |
| 'Command': '@{}RSD!OFF;FF', | |
| 'Response': '@xxxACKOFF;FF', | |
| 'Explanation': 'Turn on or off communication delay between receive and transmit sequence.'} | |
| }, | |
| 'Calibration and adjustment': { | |
| 'set_pressure_unit': { | |
| 'Command': '@{}U!MBAR;FF', | |
| 'Response': '@xxxACKMBAR;FF', | |
| 'Explanation': 'Set pressure unit setup (Torr, mbar, Pascal)'}, | |
| 'set_calibration_gas': { | |
| 'Command': '@{}GT!ARGON;FF', | |
| 'Response': '@xxxACKARGON;FF', | |
| 'Explanation': 'Set MicroPirani sensor calibration gas. (Nitrogen, Air, Argon, Helium, Hydrogen, H2O, Neon, CO2, Xenon)'}, | |
| 'perform_pirani_zero_adjustment': { | |
| 'Command': '@{}VAC!;FF', | |
| 'Response': '@xxxACK;FF', | |
| 'Explanation': 'Executes MicroPirani zero adjustment'}, | |
| 'perform_pirani_atmosphere_adjustment': { | |
| 'Command': '@{}ATM!7.60E+2;FF', | |
| 'Response': '@xxxACK;FF', | |
| 'Explanation': 'Executes MicroPirani full scale atmospheric adjustment.'}, | |
| 'perform_piezo_absolute_adjustment': { | |
| 'Command': '@{}ATD!7.60E+2;FF', | |
| 'Response': '@xxxACK;FF', | |
| 'Explanation': 'Executes Piezo absolute reading at zero differential pressure.'}, | |
| 'perform_piezo_differential_adjustment': { | |
| 'Command': '@{}ATZ;FF', | |
| 'Response': '@xxxACK;FF', | |
| 'Explanation': 'Executes Piezo differential zero adjustment'}, | |
| 'set_analog_out_1': { | |
| 'Command': '@{}AO1!10;FF', | |
| 'Response': '@xxxACK10;FF', | |
| 'Explanation': 'Set analog voltage output 1 calibration.'}, | |
| 'set_analog_out_2': { | |
| 'Command': '@{}AO1!10;FF', | |
| 'Response': '@xxxACK10;FF', | |
| 'Explanation': 'Set analog voltage output 2 calibration.'} | |
| }, | |
| 'Information setup': { | |
| 'set_user_tag':{ | |
| 'Command': '@{}UT!LOADLOCK;FF', | |
| 'Response': '@xxxACKLOADLOCK;FF', | |
| 'Explanation': 'Set transducer user tag' | |
| } | |
| }, | |
| 'User Switch': { | |
| 'set_userswitch_on_off': { | |
| 'Command': '@{}SW!ON;FF', | |
| 'Response': '@xxxACKON;FF', | |
| 'Explanation': 'Enable / disable user switch' | |
| } | |
| } | |
| } | |
| error_responses = [ | |
| ['NAK Code', 'Error', 'description'], | |
| ['8', 'Zero adjustment at too high pressure', '@253VAC!;FF'], | |
| ['9', 'Atmospheric adjustment at too low pressure', '@253ATM!7.60;FF'], | |
| ['160', 'Unrecognized message', '@253S%;FF'], | |
| ['169', 'Invalid argument', '@253EN1!of;FF'], | |
| ['172', 'Value out of range', '@253SP1!5.00E+9;FF'], | |
| ['175', 'Command/query character invalid', '@253FV!;FF'], | |
| ['180', 'Not in setup mode (locked)', '-'], | |
| ] | |
| # xxx = Transducer communication address (001 to 253. Broadcast addresses: 254, 255) | |
| broadcast_address_1 = 254 # 254 WILL cause any listening sensors to reply | |
| broadcast_address_2 = 255 # 255 will NOT cause any listening sensors to reply | |
| DEBUG = False | |
| import serial | |
| class Mks901P(object): | |
| def __init__(self, com_port_name, baud=9600): | |
| self.com_port_name = com_port_name | |
| if DEBUG: | |
| print('creating new MKS 901p object with baud of {}'.format(baud)) | |
| self.serial_port = serial.Serial(com_port_name, baudrate=baud) | |
| #self.serial_port.read() | |
| self.pressure_unit = None | |
| def get_pressure_unit(self, address=broadcast_address_1): | |
| cmd = commands['Calibration and adjustment information']['get_pressure_unit'] | |
| expect = cmd['Response'] | |
| cmd = cmd['Command'] | |
| output = self.send_cmd(cmd, expect, address) | |
| if output: | |
| self.pressure_unit = output[1] | |
| return self.pressure_unit | |
| def get_pressure_combined_4_digit(self, address=broadcast_address_1, return_address=False): | |
| cmd = commands['Pressure reading']['combined_4_digit']['Command'] | |
| expect = commands['Pressure reading']['combined_4_digit']['Response'] | |
| output = self.send_cmd(cmd, expect, address) | |
| if output and not return_address: | |
| return output[1] | |
| return output | |
| def send_cmd(self, cmd, expected_response, address): | |
| cmd = cmd.format(address) | |
| self.serial_port.write(bytes(cmd.encode())) | |
| raw_data = self.serial_port.read(len(expected_response)) | |
| data = raw_data.decode() | |
| if 'ACK' in data: | |
| addr = data[data.index('@')+len('@'):data.index('ACK')] | |
| value = data[data.index('ACK')+len('ACK'):].split(';')[0] | |
| return (addr,value) | |
| else: | |
| if DEBUG: | |
| print('no ACK received from cmd') | |
| return None | |
| import os | |
| import sys | |
| import time | |
| this_files_path = os.path.abspath(__file__) | |
| if __name__ == '__main__': | |
| import argparse | |
| parser = argparse.ArgumentParser() | |
| parser.add_argument("serial_port", help='the Windows COM port or path to a linux serial port') | |
| parser.add_argument("--find_baud", help='tries to access the sensor over all supported baud rates, prints which is successful', action="store_true") | |
| parser.add_argument("--baud", help='baud rate to connect with, defaults to 9600 (901p factory default)', type=int) | |
| parser.add_argument("-unit", help='print pressure unit with each reading', action="store_true") | |
| args = parser.parse_args() | |
| com_port = args.serial_port | |
| if args.find_baud and not args.baud: | |
| from subprocess import STDOUT, check_output, TimeoutExpired | |
| for baud in baud_supported: | |
| print("attempting to ask MKS 901p for it's baudrate using baudrate of {}".format(baud)) | |
| cmd = [sys.executable, this_files_path, com_port, '--find_baud', '--baud={}'.format(baud)] | |
| try: | |
| output = check_output(cmd, stderr=STDOUT, timeout=1) | |
| if output: | |
| output = output.decode().split(',') | |
| output = [o.strip("() '\n") for o in output] | |
| print('sensor ({}) replied with baudrate of ({})'.format(output[0], output[1])) | |
| break | |
| except TimeoutExpired: | |
| pass | |
| elif args.find_baud and args.baud: | |
| if DEBUG: | |
| print('setting up connection using baudrate of: {}'.format(args.baud)) | |
| m = Mks901P(com_port, args.baud) | |
| cmd = commands['Communication information']['get_baud_rate']['Command'] | |
| expect = commands['Communication information']['get_baud_rate']['Response'] | |
| print(m.send_cmd(cmd, expect, broadcast_address_1)) | |
| else: | |
| if args.baud: | |
| m = Mks901P(com_port, args.baud) | |
| else: | |
| m = Mks901P(com_port) | |
| unit = '' | |
| if args.unit: | |
| unit = ' {}'.format(m.get_pressure_unit()) | |
| while True: | |
| print('{}{}'.format(m.get_pressure_combined_4_digit(), unit)) | |
| time.sleep(1) |
Thanks for the very quick reply. I have succeeded in talking to it using Termite and NI Max and getting the expected replies, which is why I am confused that the simple read command doesn't work in code.
I don't see a baudrate in your code...would also try using another serial library other than pyvisa if that's not working
The default is 9600, though I did try adding the line:
self.mks946.baud_rate = 9600
It still gave me the same error.
But I did just use the 'read_bytes()' command in my get_id(self) function, so that the whole function is now:
def get_id(self):
self.mks946.write("@253SN?;FF")
response = self.mks946.read_bytes(45)
return response
The program doesn't error out and I get the response:
b'@253ACKOFF;FF@253ACKON;FF@253ACK024068025 ;FF'
It seems that after the earlier commands the buffer isn't being cleared and a carriage return is missing. Do you have some advice?
Try talking to chatgpt for coding advice, this is just standard serial comms...lots of ways to solve it like reading byte at a time or waiting for specific characters but would also read the docs for the library you're using
Okay, thanks for all the help. I think the back of problem has been broken.
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I'd try talking to it outside of python, using
screen /dev/... 9600assuming 9600 is the default baud according to the datasheet. Error just says timeout reading so it's apparently not getting data back. If you can't talk to it via screen or other serial software then would review wiring and datasheet