UNI-T UT372

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UNI-T UT372
Uni-t ut372 mugshot.png
Status supported
Source code uni-t-dmm
Counts 99999
Connectivity USB
Measurements rpm, counts
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 5 pairs of characters represent the time (least significant digit first). The final 2 pairs of characters represent the remaining segments of the display.

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.

LCD character lookup

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

Other display segments

Bit (LSB #0) First byte Second byte
0 - RPM
1 BATT COUNT
2 HOLD -
3 - -
4 LED MAX
5 - MIN
6 - AVE
7 - -

Resources