ZDS2022 Oscilloscope 100 Practical Specials 30: UART Protocol Trigger

The ZDS2022 Oscilloscope Hundred Technical Exchange Conference is still in full swing. Recently, a customer communicated with our FAE. He wanted to stably trigger the first bit of the UART data frame. He set "Edge Trigger"-"Rising Edge Trigger" in sequence, and then performed [Single] single trigger. After multiple tests, the screen occasionally showed "Not triggered on the first rising edge, but triggered on the following rising edge". What is going on?

First of all, edge triggering does not pick "edges" or only recognize the first edge, so every edge that meets the triggering conditions is likely to trigger. In fact, the customer wants to achieve the function of stably triggering the first bit of the UART data frame. The ZDS2022 oscilloscope itself contains 21 protocol trigger functions, so there is no need to use edge triggering.

Figure 1: The screen appears not triggered by the first edge

How to operate? We press the [Trigger] key, set the trigger mode to normal trigger, set the trigger type to UART type, and set the protocol parameter to start bit trigger. Then press the [Horiz] key to set the memory depth to 112Mpts. The large memory depth mode can make the protocol decoding information more complete under a large time base.

Figure 2 Setting the UART protocol trigger mode

Then press the [Decode] key, set the decoding type to UART, turn on the protocol trigger, and the protocol will be triggered according to the set conditions in the [Trigger] menu. Increase the time base. On the main interface, we can see that the trigger point is accurately located at the first bit of the UART data frame.

Figure 3 Triggering on the first rising edge and decoding results

The protocol trigger function of the ZDS2022 oscilloscope can accurately locate and help us analyze the protocol more specifically, which is very convenient!