The Uni-T UT61E+ digital multimeter can be connected to a PC through the built-in CP2110 UART-USB bridge. This repository contains a client library for its proprietary protocol.

The library is using the cross-platform HIDAPI to communicate with the device. On a Debian based system installing the following packages should be sufficient:

sudo apt install libhidapi-dev libudev-dev

The library is also available for other operating systems but this is untested.

dev, err := ut61ep.Open("")
if err != nil {
    log.Fatalf("open: %v", err)
}
message, err := dev.ReadMessage()
if err != nil {
    log.Fatalf("readMessage: %v", err)
}
log.Printf("%f %s", message.Value, message.Unit.String())

Before any communication with the multimeter can take place the CP2110 UART-USB bridge chip has to be configured by sending feature reports:

// Enable UART
0x41, 0x01

// Configure UART (9600 baud, parity=NONE, 8 Bit, hardware Flow Control disabled, stop bits short)
0x50, 0x00, 0x00, 0x25, 0x80, 0x00, 0x00, 0x03, 0x00, 0x00

Data can be requested by sending the following byte sequence:

0x06, 0xab, 0xcd, 0x03, 0x5e, 0x01, 0xd9

The device always sends two bytes at a time, the first of which is always a 1 and the second one containing the actual data byte. The following message description ignores the first byte and shows only the actual data bytes.

The device responds with a 19 byte long message. The first two bytes are constant, the following byte contains the message length and the remainder is the actual data.

01 AB CD 10 00 00 30 20 30 2e 30 38 35 30 00 01 30 30 30 03
-- ----- --    -- --    -----------------             --
 |   |    |     |  |            |                      |
 |   |    |     |  |            |                      |
 |   |    |     |  |            |                      |
 |   |    |     |  |            |                       ------ sign / sub-mode
 |   |    |     |  |             ----------------------------- value
 |   |    |     |   ------------------------------------------ range
 |   |    |      --------------------------------------------- mode
 |   |     --------------------------------------------------- length of the following message
 |    -------------------------------------------------------- constant preamble
  ------------------------------------------------------------ message type

For many of the bytes only the least significant 4-bits are relevant and the most significant 4-bits are 0x30.

• This library was inspired by a similar project for a different Uni-T multimeter
• CP2110 datasheet