As someone who has never had an opportunity to play with it, I’m fascinated by what people are doing with PIO. In many cases it seems to be a ‘good enough’ FPGA on absurdly cheap hardware.
Honestly what they're describing can be done on any MCU without PIO - set up clock division/PLL to provide ADC clock, use that same clock for timer source, set up a timer channel to trigger the pulse, set up a timer channel to trigger ADC DMA capture start, start the timer.
Congrats, now you have capture synchronized to pulse start "providing the sub-microsecond timing needed for ultrasound acquisition".
I think you miss understood the challenge. They are using a 60Msps ADC with a parallel port interface. The challenge is capturing the 600Mbit/s of data and having enough CPU and memory bandwidth to do anything useful with it.
If your microcontroller has a parallel port interface, you would use the clock setup you described. This works, I've done it before, but there was very little CPU left to do anything useful with the data.
It's neat that they used the PIO, its demonstrating how that peripheral fills a niche where you things that might have been impossible without an FPGA, suddenly become doable on a microcontroller.
and one has a complete hardware solution?
Congrats, now you have capture synchronized to pulse start "providing the sub-microsecond timing needed for ultrasound acquisition".
If your microcontroller has a parallel port interface, you would use the clock setup you described. This works, I've done it before, but there was very little CPU left to do anything useful with the data.
It's neat that they used the PIO, its demonstrating how that peripheral fills a niche where you things that might have been impossible without an FPGA, suddenly become doable on a microcontroller.