Development of time-division multiplexing module for multi-channel ultrasond detector

This is a undergraduate project I assists guiding, with the goal of developing a multi-channel multiplexing module to expand a multi-channel ultrasound testing device. Through a selection process, different ultrasound probes are connected to the acquisition channels for sampling according to a specified timing sequence, allowing multiple ultrasound probes to share the same acquisition module. This not only extends the channels but also reduces manufacturing costs.

The system block diagram of the time-division multiplexing module of the multi-channel ultrasound detector designed for this system is shown in Fig 1.

The system utilizes the ZYNQ-7000 as the main control module. On one hand, this module needs to receive the timing logic for channel selection from the host computer. On the other hand, the ZYNQ within the module is responsible for accomplishing the following three tasks:

1. Generating trigger signals.
2. Generating channel selection signals to control Mux-8, activating specific channels in accordance with the timing sequence.
3. Controlling the ADC for acquiring analog signals.

The PCB design and physical diagram of the selector circuit are as shown in Fig 2 and Fig 3.

In this project, circuit design constitutes approximately 30% of the overall work. The primary focus, which accounts for 70% of the project, involves the development of time-division multiplexing timing logic.

The ARM processor in the ZYNQ communicates with the host computer through a UART serial interface to receive custom configuration data packets. The FPGA reads the configuration data from the ARM and uses it to modify the timing logic. This configuration information includes various parameters:

1. trigger start/stop
2. the number of channels to be selected
3. the frequency of the detection cycle
4. the duty cycle of the trigger signal
5. the channel selection sequence within a single detection cycle.