Difference between revisions of "UNI-T UT372"

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== Protocol ==
== Protocol ==


The MCU transmits serial data to the CH9325 at 2400 baud. A packet is 27 bytes of ASCII data ending in CR, LF. The meaning of each part of the ASCII data is still to be decoded.
The MCU transmits serial data to the CH9325 at 2400 baud. A packet is 27 bytes of ASCII data ending in CR, LF.
 
The packet is processed to turn it into a valid hex string - any character with an ASCII value above 0x39 is shifted up by 7 characters, putting it into the range 'A' to 'F'.
 
The first character seems to be ignored. The next 5 pairs of characters represent the RPM (least significant digit first). The next 4 pairs of characters represent the time (least significant digit first). The remaining characters are unknown at this point.
 
Each pair of characters, when interpreted as a single hex byte, is a bitfield representing the on/off state of segments on the display. A look-up table is provided below. Setting the most significant bit indicates that a decimal point is placed after that digit.
 
{| border="0" class="alternategrey sigroktable sortable"
|-
! style="width: 5em; text-align: left;" | String
! style="text-align: left;" | Hex Byte
! style="text-align: left;" | Character
|-
| "7;"
| 0x7B
| 0
|-
| "60"
| 0x60
| 1
|-
| "5>"
| 0x5E
| 2
|-
| "7<"
| 0x7C
| 3
|-
| "65"
| 0x65
| 4
|-
| "3="
| 0x3D
| 5
|-
| "3?"
| 0x3F
| 6
|-
| "70"
| 0x70
| 7
|-
| "7?"
| 0x7F
| 8
|-
| "7="
| 0x7D
| 9
|-
| "0;"
| 0x0B
| L
|-
|}


== Resources ==
== Resources ==

Revision as of 21:57, 1 March 2015

UNI-T UT372
UT372 front.jpg
Status in progress
Connectivity USB
Website uni-trend.com

The UNI-T UT372 is a digital tachometer with USB connectivity.

Hardware

The unit includes a built in laser pointer for aiming at a reflective target, and a tripod fitting to allow stable mounting.

Photos

Protocol

The MCU transmits serial data to the CH9325 at 2400 baud. A packet is 27 bytes of ASCII data ending in CR, LF.

The packet is processed to turn it into a valid hex string - any character with an ASCII value above 0x39 is shifted up by 7 characters, putting it into the range 'A' to 'F'.

The first character seems to be ignored. The next 5 pairs of characters represent the RPM (least significant digit first). The next 4 pairs of characters represent the time (least significant digit first). The remaining characters are unknown at this point.

Each pair of characters, when interpreted as a single hex byte, is a bitfield representing the on/off state of segments on the display. A look-up table is provided below. Setting the most significant bit indicates that a decimal point is placed after that digit.

String Hex Byte Character
"7;" 0x7B 0
"60" 0x60 1
"5>" 0x5E 2
"7<" 0x7C 3
"65" 0x65 4
"3=" 0x3D 5
"3?" 0x3F 6
"70" 0x70 7
"7?" 0x7F 8
"7=" 0x7D 9
"0;" 0x0B L

Resources