Difference between revisions of "Victor 70C"

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| Flags (only bit 0 used)
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| Value factors and extra measurement modes
| Value factors and extra measurement modes
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| 0
| µ (Micro)
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| 1
| m (Milli)
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| 2
| k (Kilo)
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| 3
| M (Mega)
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| 4
| Continuity (in combination with resistance mode in byte 3)
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| 5
| Diode (in combination with voltage mode in byte 3)
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| 6
| Duty cycle measurement mode.
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| 7
| unused.


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| 5
| 5
|  
|  
|  
| Extra flags and value factors
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| 0
| unused.
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| 1
| unused.
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| 2
| Max measurement mode.
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| 3
| Min measurement mode.
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| 4
| unused.
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| 5
| unused.
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| 6
| n (Nano)
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| 7
| unused.
 


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| 6
| 6
|  
|  
|  
| Flags
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| 0
| unused.
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| 1
| unused.
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| 2
| Auto-ranging mode.
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| 3
| DC measurement.
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| 4
| AC measurement.
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| 5
| Relative measurement.
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| 6
| Hold mode.
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| 7
| unused.


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Revision as of 13:09, 18 August 2012

Victor 70C

The Victor 70C is a 4000 counts, CAT II handheld digital multimeter with USB connectivity. It is also sold as the EZA EZ-735

See Victor 70C/Info for more details (such as lsusb -vvv output) about the device.

Hardware

Photos

  • Device, front

  • PCB, front

  • PCB, bottom

  • DMM/LCD chip

  • NXP HEF4066BT

  • Microchip TC7660E

  • TI 27L2C

  • LCD

Protocol

The device registers on the USB host as a HID-class device. The protocol payload is 14 bytes of data which can be read from endpoint 1, at no more than 1 Hz.

The 14-byte chunk is somewhat obfuscated. To deobfuscate, subtract the ASCII value of the following string from each of the 14 bytes in turn: jodenxunickxia. Then reshuffle the bytes into different positions, according to the following table:

Original position  0  1  2  3  4  5  6  7  8  9 10 11 12 13
Final position  6 13  5 11  2  7  9  8  3 10 12  0  4  1

The deobfuscated payload is then structured as follows:

Byte Bit Value
0 Unused (always contains 0x50)
1 Unused (always contains 0xb0)
2 Flags
0 Minus
1-7 Unused.
3 Major measurement modes
0 Voltage measurement mode, combined with AC or DC flags in byte 6. In combination with the Diode flag in byte 4, signifies diode testing mode.
1 Current measurement mode, combined with AC or DC flags in byte 6.
2 Resistance measurement mode. In combination with the Continuity flag in byte 4, signifies continuity testing mode.
3 Unused.
4 Frequency measurement mode.
5 Capacitance measurement mode.
6 Temperate measurement mode, in Celcius.
7 Temperature measurement mode, in Fahrenheit.
4 Value factors and extra measurement modes
0 µ (Micro)
1 m (Milli)
2 k (Kilo)
3 M (Mega)
4 Continuity (in combination with resistance mode in byte 3)
5 Diode (in combination with voltage mode in byte 3)
6 Duty cycle measurement mode.
7 unused.
5 Extra flags and value factors
0 unused.
1 unused.
2 Max measurement mode.
3 Min measurement mode.
4 unused.
5 unused.
6 n (Nano)
7 unused.


6 Flags
0 unused.
1 unused.
2 Auto-ranging mode.
3 DC measurement.
4 AC measurement.
5 Relative measurement.
6 Hold mode.
7 unused.
7 Decimal point position
8 Unused (always contains 0x04)
9
10
11
12
13 Unused (always contains 0xd4)

Resources

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