Using Hardware or Serial Interface to Configure During Initialization

pbiyengar

I am trying to configure the Quarto to perform multiple PID control loops. However, I do not have access to the number of loops per qNimble box I will need to activate a priori, that is, I don't know how many ADCs need to be reading. To optimize bandwidth, I'd like to condition the ADC configuration in void setup(void) such that, depending on an input, the device will qNimble a certain number of the ADCs. Moreover, I want this conditioning signal to be native, i.e., I don't want to have to drive the box with an external signal from an FPGA. My current thought is to configure some of the Digital I/O pins for output and some for input, and then just tie them together as needed; then each ADC configuration statement will be nested within an if statement conditioned on the state of the corresponding pin. Is this a valid method? Do I have read/write access to the pins during the initialization/setup? If not, is there a way to pause the setup and wait for a serial command to tell it how many or which ADCs to configure?

Edit: I think the SD card interface would allow me to store information about configuration which I could then read out during the setup method. However, I'd prefer not to rely on an SD card since that can be taken out or lost easily. Sorry to make this difficult.

Ben

So can definitely change the ADC configuration on demand by running the configureADC function. If I'm understanding correctly, I think something like:

changeConfig(uint8_t channels) {
//ADC1
  if (channels & 0x01) {
    //ADC1 is active:
   configureADC(1,10,0,BIPOLAR_10V,getADC1);
  } else {
    disableADC(1);
  }
  
  //ADC2
  if (channels & 0x02) {
    //ADC2 is active:
   configureADC(2,10,0,BIPOLAR_10V,getADC2);
  } else {
    disableADC(2);
   }
//continue for ADC3 and ADC4
}

Then you can run changeConfig(0) to turn off all the ADC's. changeConfig(15) to turn them all one, or changeConfig(8) to just turn on ADC4. You can then use qCommand to call that function based on a serial command. If you need faster response then serial communication, you can use one of the triggers to fire an interrupt when the line goes high (see OutputPatternOnTrigger example for reference). Then you can either walk through different modes, one per trigger, or read either a variable set by a serial command, or a few of the GPIO pins to determine which mode to go to.

Yes, you have read-write access to all the GPIO and trigger pins in the setup() function a beyond, so you can definitely use them for initialization if you want. But I think doing no ADC initialization in setup() might serve you better and then run the configureADC on-demand based on an external digital line or a serial command.

I hope this makes sense. Please let me know if you have any questions.

pbiyengar

Thank you very much! This is exactly what I'm looking for.

pbiyengar

A small follow-up, if I may - I am a bit worried about storing the PID gain constants and ADC activation status in case of power cycling. Is there a method to access the non-volatile memory of the processor? e.g., how one might store a simple bit string in the EEPROM of an Arduino?

Ben

Yes, you can do that. I don't have it well documented yet. But the functions you'll want to use are:

uint16_t readNVM(uint32_t address);
void readNVMblock(void* data,uint16_t length, uint32_t start_addr);
void writeNVMpages(void* data,uint16_t data_size, uint16_t first_page);

The Quarto has 96kB of user-accessible non-volatile memory (NVM) (often called eeprom). This is broken down into 768 pages with each page 128 bytes long. readNVM() reads a single 16-bit data point from the non-volatile memory (NVM) (often called eeprom).

One thing to note is that at the hardware level, you have to write a full page at a time. So if you use the writeNVMpages and only write to part of a page, the rest of that page will get erased. If you want to change only one value, probably the best thing to do is use readNVMblock to read the full page to a local variable, edit what you want to change and the write page that full page.

I'll try to get this documented on the website, but let me know if you have any questions / issues.

Ben

I added some basic documentation:
https://qnimble.com/Quarto/Functions/Memory