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 | 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
 | |
| Status | in progress |
|---|---|
| Connectivity | USB |
| Website | uni-trend.com |
The UNI-T UT372 is a digital tachometer with USB connectivity.
Hardware
- Silicon Labs C8051F313 MCU
- Holtek HT1621B LCD controller
- WCH CH9325 USB UART interface
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 |