Difference between revisions of "Victor 70C"

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The deobfuscated payload is then structured as follows:
The deobfuscated payload is then structured as follows:
{| border="0" width="50%" style="font-size: smaller" class="alternategrey sortable sigroktable"
{| border="0" width="95%" style="font-size: smaller" class="alternategrey sortable sigroktable"
|-
|-
! style="width: 3em;" | Byte
! style="width: 3em;" | Byte
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| 1
| 1
|
|
| Unused (always contains 0x50)
| Unused (always contains 0xb0)


|-
|-
| 2
| 2
|
|
| Flags
| Flags (only bit 0 used)


|-
|-
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|
|
| Major measurement modes
| 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.


|-
|-

Revision as of 12:56, 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 (only bit 0 used)
0 Minus
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
5
6
7 Decimal point position
8 Unused (always contains 0x04)
9
10
11
12
13 Unused (always contains 0xd4)

Resources

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