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5.3.3 - Feedback (and FeedbackAlt)

A very useful function that writes/reads almost every I/O on the LabJack UE9.

Note: Feedback command should not be called while streaming. FeedbackAlt with no analog inputs is allowed.

Table 5.3.3-1. Feedback Command Response

Feedback Command:    
Byte    
0 Checksum8  
1 0xF8  
2 0×0E  
3 0×00  
4 Checksum16 (LSB)  
5 Checksum16 (MSB)  
6 FIOMask  
7 FIODir  
8 FIOState  
9 EIOMask  
10 EIODir  
11 EIOState  
12 CIOMask  
13 CIODirState  
    Bits 7-4: Direction
    Bits 3-0: State
14 MIOMask  
15 MIODirState  
    Bits 6-4: Direction
    Bits 2-0: State
16 DAC0 (LSB)  
17 DAC0  
    Bit 7: Enabled
    Bit 6: Update
    Bits 3-0: Upper 4 bits output
18 DAC1 (LSB)  
19 DAC1  
    Bit 7: Enabled
    Bit 6: Update
    Bits 3-0: Upper 4 bits output
20-21 AINMask  
22 AIN14ChannelNumber  
23 AIN15ChannelNumber  
24 Resolution  
25 SettlingTime  
26 AIN1_0_BipGain  
27 AIN3_2_BipGain  
28 AIN5_4_BipGain  
29 AIN7_6_BipGain  
30 AIN9_8_BipGain  
31 AIN11_10_BipGain  
32 AIN13_12_BipGain  
33 AIN15_14_BipGain  
     
     
Response:    
Byte    
0 Checksum8  
1 0xF8  
2 0×1D  
3 0×00  
4 Checksum16 (LSB)  
5 Checksum16 (MSB)  
6 FIODir  
7 FIOState  
8 EIODir  
9 EIOState  
10 CIODirState  
11 MIODirState  
12-13 AIN0  
14-15 AIN1  
16-17 AIN2  
18-19 AIN3  
20-21 AIN4  
22-23 AIN5  
24-25 AIN6  
26-27 AIN7  
28-29 AIN8  
30-31 AIN9  
32-33 AIN10  
34-35 AIN11  
36-37 AIN12  
38-39 AIN13  
40-41 AIN14  
42-43 AIN15  
44-47 Counter0  
48-51 Counter1  
52-55 Timer0  
56-59 Timer1  
60-63 Timer2  
  • IOMask: Mask each bit of digital I/O individually. If a bit is 1, then the new direction and state values will be written to that bit of I/O. If a bit is 0, only a read of state and direction will be done.
  • IODir: 0 is input, and 1 is output.
  • IOState: As a write parameter, only has an effect if a line is set to output. For each bit, 0 is output-low, and 1 is output-high. As a read parameter, it returns the current input state of each line where 0 is low and 1 is high.
  • DAC#: The UE9 has 12-bit analog outputs, so pass an output value between 0 and 4095, plus set bits 6 and 7 of the high byte accordingly. Bit 6 specifies whether the given DAC will be updated with the new value. If Bit7 is set on either DAC, then both are enabled. To disable the DACs (set to high-impedance), bit 7 must be 0 for both DACs.
  • AINMask: If a bit is 0, the corresponding channel will not be acquired (saving time), and will return 0 as a reading.
  • AIN14/15ChannelNumber: Generally used to choose one of the internal channels, but any channel can be used.
  • Resolution: Determines the resolution setting for all analog inputs (12-17). See Sections 2.7, 3.1, and 3.2. This function does not support the high-resolution converter on the UE9-Pro.
  • SettlingTime: Adds extra settling time before acquiring each channel. The extra delay is this value multiplied by about 5 microseconds.
  • BipGain: Contains the bipolar setting and gain options for two analog input channels. The high nibble controls the higher channel number. The high bit of each nibble is the bipolar option and the lower 3 bits of each nibble are the gain index. Following are the nibble values for various gains:

Table 5.3.3-2. Nibble values for various gains

Gain Unipolar Bipolar
*1 0×00 0×08
*2 0×01 NA
*4 0×02 NA
*8 0×03 NA
  • AIN#: Returns raw analog input conversions. Regardless of Resolution, the value returned is 0-65520, where 0 is the minimum (unsigned, not 2’s complement).
  • Counter#: Returns the current count from the counters if enabled. Use the function TimerCounter to enable and configure the counters.
  • Timer#: Returns the values from the first 3 enabled timer modules. Use the function TimerCounter to enable and configure the timer modules.

The LabJackUD driver for Windows uses a modified version of the Feedback function called FeedbackAlt. This modified function has additional parameters added to specify channel numbers for all 16 analog input reads, making it useful when using extended channels or more than 2 internal channels.

The command for FeedbackAlt is the same as Feedback, except that AINxChannelNumber parameters are added for channels 0-13 (new bytes 34-47). The command number (byte 3) changes to 0x01 and the number of data words (byte 2) changes to 0x15.

The response for FeedbackAlt is the same as Feedback, except that the counter/timer reads are removed, and thus the response is 44 bytes long. The command number (byte 3) changes to 0x01 and the number of data words (byte 2) changes to 0x13.

The order of execution in hardware for either function is:

  1. Write digital I/O.
  2. Read digital I/O.
  3. Write analog outputs.
  4. Read analog inputs.
  5. Read timers and counters (skipped in FeedbackAlt).

4 comments

Is it possible for you to write a simple example, using this low-level function?

Thanks!

We have many examples already prepared. You can download them here.

Yes, I saw those, but was looking for some more ue9-specific examples, esp on the getFeedback method.There was a post from your support team suggesting there might be fewer ue9 examples then you wanted, so I was hoping this request might post me to new material.

Thanks anyway, I'll keep plugging away.

Red

 

Some languages have more examples than others. You might look in other archives. LabView has a lot of low level examples.