Driver for Measurement Computing Multi-Function Devices

Table of Contents

• Introduction
• Configuration
• Databases
• Wiring example for USB-2408-2AO
• Wiring example for USB-1608GX-2AO
• Performance measurements

Introduction

This is an EPICS driver for the multi-function devices from Measurement Computing These multi-function devices support support analog in, thermocouple in, analog out, binary I/O, counters, and timers. Not all devices have all of these capabilities. The driver is written in C++, and consists of a class that inherits from asynPortDriver, which is part of the EPICS asyn module.

The driver is written to be general, so that it can be used with any Measurement Computing multi-function module. It uses the introspection capabilities of their UL library to query many of the device features. However, there are some features that cannot be queried, so the driver does require small modifications to be be used with a new model. The models that the driver currently supports are:

• USB-1608G and USB-1608GX-2AO
• E-1608
• USB-2408-2AO
• E-TC
• TC-32
• USB-1208LS, USB-1208FS, and USB-231
• E-DIO24

USB-1608GX-2AO

Photo of USB-1608GX-2AO

This module costs $799 and has the following features:

• 16-bit analog inputs
  • 16 single-ended channels or 8 differential channels
  • Programmable per-channel range: +-1V, +-2V, +-5V, +-10V
  • 500 kHz total maximum input rate, i.e. 1 channel at 500 kHz, 8 channels at 62.5 kHz, etc.
  • Internal or external trigger. External trigger shared with analog outputs.
  • Internal or external clock, input and output signals.
  • 4 kSample input FIFO, unlimited waveform length
• 16-bit analog outputs
  • 2 channels, fixed +-10V range
  • 500 kHz total maximum output rate, i.e. 1 channel at 500 kHz, 2 channels at 250 kHz
  • Internal or external trigger. External trigger shared with analog inputs.
  • Internal or external clock, input and output signals
  • 2 kSample output FIFO, unlimited waveform length
• Digital inputs/outputs
  • 8 signals, individually programmable as inputs or outputs
• Pulse generator
  • 1 output
  • 64MHz clock, 32-bit registers
  • Programmable period, width, number of pulses, polarity
• Counters
  • 2 inputs
  • 20 MHz maximum rate, 32-bit registers

More information can be found in the USB-1608GX-2AO product description.

The USB-1608G is very similar to the USB-1608GX-2AO except that it does not have any analog outputs and the analog inputs are limited to 250 kHz rather than 500 kHz. More information can be found in the USB-1608G product description.

The following is the main medm screen for controlling the USB-1608GX-2AO.

1608G_module.adl

E-1608

Photo of E-1608

This module costs $525 and has the following features:

• 16-bit analog inputs
  • 8 single-ended channels or 4 differential channels
  • Programmable per-channel range: +-1V, +-2V, +-5V, +-10V
  • 250 kHz total maximum input rate, i.e. 1 channel at 250 kHz, 2 channels at 125 kHz, etc.
  • Internal or external trigger.
  • Internal or external clock for input signals.
  • Input FIFO, unlimited waveform length
• 16-bit analog outputs
  • 2 channels, fixed +-10V range
  • No output waveform capability
• Digital inputs/outputs
  • 8 signals, individually programmable as inputs or outputs
• Counter
  • 1 input
  • 10 MHz maximum rate, 32-bit register

More information can be found in the E-1608 product description.

The following is the main medm screen for controlling the E-1608.

E1608_module.adl

USB-2408-2AO

Photo of USB-2408-2AO

This module costs $699 and has the following features:

• 24-bit analog inputs
  • 16 single-ended channels or 8 differential channels
  • Programmable per-channel range: 8 ranges from +-0.078V to +-10V
  • Thermocouple support for 8 channels with cold-junction compensation. Types J, K, T, E, R, S, B, or N.
  • 1 kHz total maximum input rate, i.e. 1 channel at 1 kHz, 8 channels at 125 Hz, etc.
  • Input FIFO, unlimited waveform length
• 16-bit analog outputs
  • 2 channels, fixed +-10V range
  • 1000 Hz total maximum output rate, i.e. 1 channel at 1000 Hz, 2 channels at 500 Hz
  • Output FIFO, unlimited waveform length
• Digital inputs/outputs
  • 8 signals, individually programmable as inputs or outputs
• Counters
  • 2 inputs
  • 1 MHz maximum rate, 32-bit registers

More information can be found in the USB-2408-2AO product description.

The following is the main medm screen for controlling the USB-2408-2AO.

2408_module.adl

E-TC

Photo of E-TC

This module costs $505 and has the following features:

• Ethernet interface.
• 8 thermocouple inputs
  • 8 channels with cold-junction compensation. Types J, K, T, E, R, S, B, and N.
  • 4 samples/s.
• Digital inputs/outputs
  • 8 signals, individually programmable as inputs or outputs
• Counters
  • 1 input
  • 10 MHz maximum rate, 32-bit register

More information can be found in the E-TC product description.

The following is the main medm screen for controlling the E-TC.

ETC_module.adl

TC-32

Photo of TC-32

This module costs $1999 and has the following features:

• USB and Ethernet interfaces, either can be used.
• 32 thermocouple inputs
  • 32 channels with cold-junction compensation. Types J, K, T, E, R, S, B, and N.
  • 3 samples/s if reading all 32 channels, faster if reading fewer.
• Digital inputs
  • 8 digital inputs, switch-selectable pullup resistor
• Digital outputs
  • 32 digital inputs, switch-selectable pullup resistor
  • Each output can either be controlled by software or can be controlled by the alarm status of the corresponding thermocouple. Flexible alarm configuration, i.e. hysteresis.

More information can be found in the TC-32 product description.

The following is the main medm screen for controlling the TC-32.

TC32_module.adl

USB-1208LS

Photo of USB-1208LS

This module costs $129 and has the following features:

• 12-bit analog inputs
  • 4 differential channels
  • Programmable per-channel range: 8 ranges from +-1V to +-20V
  • 50 Hz maximum sampling rate. The module has a trigger input that allows higher sampling rates, but this is not yet supported in the EPICS driver.
• 10-bit analog outputs
  • 2 channels, fixed 0 to +5V range
  • 100 Hz maximum input rate
• Digital inputs/outputs
  • 16 signals, programmable as inputs or outputs in groups of 8
• Counters
  • 1 input
  • 1 MHz maximum rate, 32-bit register

More information can be found in the USB-1208LS product description.

The USB-1208HS and USB-231 are similar devices but with higher performance.

The following is the main medm screen for controlling the USB-1208LS.

USB1208LS_module.adl

E-DIO24

Photo of E-DIO24

This module costs $320 and has the following features:

• Digital inputs/outputs
  • 24 signals, individuaully programmable as inputs or outputs
• Counters
  • 1 input
  • 10 MHz maximum rate, 32-bit register

More information can be found in the E-DIO24 product description.

Configuration

The following lines are needed in the EPICS startup script for the multifunction driver.

## Configure port driver
# MultiFunctionConfig(portName,        # The name to give to this asyn port driver
#                     boardNum,        # The number of this board assigned by the Measurement Computing Instacal program 
#                     maxInputPoints,  # Maximum number of input points for waveform digitizer
#                     maxOutputPoints) # Maximum number of output points for waveform generator
MultiFunctionConfig("1608G_1", 1, 1048576, 1048576)
dbLoadTemplate("1608G.substitutions.big")

The measComp module comes with example iocBoot/ directories that contain example startup scripts and example substitutions files. These directories are iocUSB1208, iocUSB1608G, iocUSB1608G-2A0, iocUSB2408, iocUSB231, iocUSBC9513, iocUSBCTR, and iocMeasCompDemo.

Databases

The following tables list the database template files that are used with the multi-function modules.

Analog I/O Functions

The following is the medm screen for controlling the analog input records for the USB-1608GX-2AO. Note that the engineering units limits (EGUL and EGUF) do not have to be in volts, they can be in any units such as "percent", "degrees", etc.

measCompAiSetup.adl

The following is the medm screen for controlling the analog output records for the USB-1608GX-2AO. Note that the engineering units limits (EGUL and EGUF) do not have to be in volts, they can be in any units such as "percent", "degrees", etc. The drive limits can be more restrictive than the full +-10V output range of the analog outputs.

measCompAoSetup.adl

Temperature Functions

The following is the main medm screen for configuring the analog/temperature inputs on the USB-2408-2AO.

measCompTemperatureSetup.adl

Digital I/O Functions

Pulse Generator Functions (these are called "timers" in Measurement Computing's documentation)

Waveform Digitizer Functions

Plot of a digitized waveform of someone speaking into a microphone

Waveform Generator Functions

Plot of an internal predefined waveform (sin wave)

Plot of a user-defined waveform (sum of sin and cos waves)

Trigger Functions

Box for thermocouple connections for USB-2408-2A0

The following photo shows a box we built to house the USB-2408-2AO and provide I/O connections. .

USB-2408 box, top view

USB-2408 box, side views

Wiring USB-1608GX-2AO to BCDA BC-020 LEMO Breakout Panels

The following photo shows the BCDA BC-020 LEMO breakout panels wired to the USB-1608GX-2AO. These are the lower 2 BC-020 panels in this photo. A BC-020 with a BC-026 daughter card is used for the analog signals (lower left), and a BC-020 with a BC-087 daughter card for the digital signals (lower right).

BC-020 LEMO breakout panels

USB-1608GX-2AO Wiring to Two BCDA BC-020 LEMO Breakout Panels

      Digital I/O using BC-087 daughter card

50-pin ribbon      USB-1608GX      BC-020   EPICS Function
connector pin    screw terminal   connector
 1                DIO0               J1     Digital I/O bit 0 
 2                DIO1               J2     Digital I/O bit 1
 3                DIO2               J3     Digital I/O bit 2
 4                DIO3               J4     Digital I/O bit 3
 5                DIO4               J5     Digital I/O bit 4
 6                DIO5               J6     Digital I/O bit 5
 7                DIO6               J7     Digital I/O bit 6
 8                DIO7               J8     Digital I/O bit 7
 9                 TMR               J9     Pulse generator output
10                 GND              J10     Grounded to avoid cross-talk
11                CTR0              J11     Counter 1 input
12                 GND              J12     Grounded to avoid cross-talk
13                CTR1              J13     Counter 2 input
14                 GND              J14     Grounded to avoid cross-talk
15                TRIG              J15     Trigger input for waveform generator and waveform digitizer
16                 GND              J16     Grounded to avoid cross-talk
17               A0CK0              J17     Waveform generator clock out
18                 GND              J18     Grounded to avoid cross-talk
19               A0CKI              J19     Waveform generator clock in
20                 GND              J20     Grounded to avoid cross-talk
21               AICK0              J21     Waveform digitizer clock out
22                 GND              J16     Grounded to avoid cross-talk
23               AICKI              J17     Waveform digitzer clock in
50                 GND           J1-J32     LEMO connectors outer shells

 
         Analog I/O using BC-026 daughter card

50-pin ribbon      USB-1608GX      BC-020   EPICS Function
connector pin    screw terminal   connector
 1                CH0H               J1     Analog input 1 +
 2                CH0L               J1     Analog input 1 -
 3                AGND              N.C     Analog ground
 4                CH1H               J2     Analog input 2 +
 5                CH1L               J2     Analog input 2 -
 6                AGND              N.C     Analog ground
 7                CH2H               J3     Analog input 3 +
 8                CH2L               J3     Analog input 3 -
 9                AGND              N.C     Analog ground
10                CH3H               J4     Analog input 4 +
11                CH3L               J4     Analog input 4 -
12                AGND              N.C     Analog ground
13                CH4H               J5     Analog input 5 +
14                CH4L               J5     Analog input 5 -
15                AGND              N.C     Analog ground
16                CH5H               J6     Analog input 6 +
17                CH5L               J6     Analog input 6 -
18                AGND              N.C     Analog ground
19                CH6H               J7     Analog input 7 +
20                CH6L               J7     Analog input 7 -
21                AGND              N.C     Analog ground
22                CH7H               J8     Analog input 8 +
23                CH7L               J8     Analog input 8 -
24                AGND              N.C     Analog ground
25               AOUT0               J9     Analog output 1
26                AGND               J9     Analog ground
27                AGND              N.C     Analog ground
28               AOUT1              J10     Analog output 1
29                AGND              J10     Analog ground

Note: the "Analog input N +" lines are connected to the Lemo center pin, 
and the "Analog input N -" lines are connected to the Lemo shell.

Performance measurements

The following summarizes a simple test of the precision and accuracy of the analog outputs and analog inputs of the USB-1608GX-2AO. The test configuration was with Analog Output 0 connected to Analog Input 0, and also to a Keithley 2700 digital multimeter. The Keithley is a 6.5 digit (22 bit) device, so it can be used to measure the accuracy of the USB-1608GX-2AO analog output, and provide the "true" value to measure the accuracy of the analog input. The 1608GX analog inputs records and the Keithley input had SCAN=0.1 second, so new readings were being made at 10Hz. The following IDL test program was used to drive the analog output from -10V to +10V in 0.1V steps. 10 readings were made of the 1608GX analog inputs, and one reading of the Keithley at each voltage step. These tests were done with the +-10V range of the analog outputs and analog inputs. Since these are 16-bit devices, one bit is 20V/65536 = 0.000305 volts.

pro test_analog_performance_1608,  ao=ao, ai=ai, min_volts=min_volts, max_volts=max_volts, $
                                   step_volts=step_volts, num_samples=num_samples, delay=delay, $
                                   keithley=keithley, results
                                   
  if (n_elements(ao)          eq 0) then ao          = '1608G:Ao1'
  if (n_elements(ai)          eq 0) then ai          = '1608G:Ai1'
  if (n_elements(min_volts)   eq 0) then min_volts   = -10.0
  if (n_elements(max_volts)   eq 0) then max_volts   =  10.0
  if (n_elements(step_volts)  eq 0) then step_volts  = 0.1
  if (n_elements(num_samples) eq 0) then num_samples = 10 
  if (n_elements(delay)       eq 0) then delay       = 0.1
  if (n_elements(keithley)    eq 0) then keithley    = '13LAB:DMM2Dmm_raw.VAL'

  output = min_volts
  samples = dblarr(num_samples)
  num_points = ((max_volts - min_volts) / step_volts + 0.5) + 1
  results = dblarr(4, num_points)
  for i=0, num_points-1 do begin
    output = min_volts + i*step_volts
    t = caput(ao, output)
    wait, 2*delay
    for j=0, num_samples-1 do begin
      wait, delay
      t = caget(ai, temp)
      samples[j] = temp
    endfor
    m = moment(samples)
    results[0,i] = output
    results[1,i] = m[0]
    results[2,i] = sqrt(m[1])
    t = caget(keithley, temp)
    results[3,i] = temp
    print, results[0,i], results[1,i], results[2,i], results[3,i]
  endfor
end

The following plot shows the difference of the nominal 1608GX analog output voltage from the Keithley 2700 reading. The mean error is 0.000312V, or just over 1 bit. The RMS error is 0.000203V, or less than 1 bit.

The following plot shows the difference of the mean of 10 readings of the 1608GX analog input voltage from the Keithley 2700 reading. The mean error is 0.000106V, less than 1 bit. The RMS error is 0.000259V, also less than 1 bit.

The following plot shows the standard deviation of 10 readings of the 1608GX analog input voltage. The values range from about 0.001V (~3 bits) at +-10V to less than 0.0003V (1 bit) between -2 and +2V.

The following table contains all of the results from the tests.