How does the LPC1788FBD144 chip configure the ADC function to collect two signals simultaneously?

Question

Now I need to configure the AD sampling feature of the LPC1788FBD144 chip, which requires the ability to read both signals simultaneously. However, there is only one ADC in the chip, how to sample two signals. By looking at the chip manual, you know that the chip has an ADC mouth with 8 channels at the same time. But in software mode, only one channel can be sampled at a time. If in the hardware scan mode, which bits of the 8 channels are set to 1, the sampling values of these channels can be read. I suspect that you may need to configure a hardware scan mode to sample both signals simultaneously.

My question is:

1、LPC1788FBD144 chip has only one ADC mouth, how to sample two signals simultaneously?

2、The first 8 bits in the AD control register of LPC1788FBD144 chip are the selection and input channels. In the software mode, only one can be set to 1. In the hardware scan mode, any value containing 1-8 can be written into that bit. I now need to collect two signals, which will require two channels, so two channels must be configured in the hardware scan mode. So what is the hardware scan pattern? How to start the hardware scan mode?

Answer 1

LPC1788FBD144 chip has only one ADC mouth, how to sample two signals simultaneously?

You can't read them exactly at the same time. Microcontroller SA ADC:s work by connecting one pin at a time to the actual ADC. How fast it can do this depends on sample rate and ADC clock. According to the product brief of that part, it has a conversion rate of up to 400kHz, meaning you'll get at best a 2.5us delay between samples. Check the manual for details.

This is usually good enough for the vast majority of applications. If you have tighter real-time requirements than that, you should probably be using a DSP instead of some general-purpose microcontroller.

You could of course get a MCU with two ADC:s, or use an external ADC. But I kind of doubt that your real-time specification "read at exactly the same time" makes sense. What is the purpose of the ADC read?

As for how to use your specific ADC, I don't know, but typically you'd set it up for "continuous conversion", where it keeps cycling through the channels you have enabled and write the results to their corresponding data input registers.