Adc Sampling running out of memory?

curiosul — Mon, 12 Nov 2018 10:16:05 GMT

Hello!

I am trying to make a basic filter for ADC measurements. The idea is provide the average of previous 1000 samples as an output. To store the samples I have used a circular buffer with 1000 elements. When a new element is added the last element is removed; this way I always have stored last 1000 ADC samples so I can easily get the average.

The problems is that I will have to store samples for multiple ADC channnels. For 10 ADc channels would be 10 * 1000 samples/channel = 10k samples stored in memory at any moment of time.

I have made my program and it works only when I initialize buffers with only 10 samples (or less) per channel. When I use a bigger number of samples the program is just failing to start. I suspect that I am running out of memory.

Initial memory configuration was:

HEAP_SIZE = DEFINED(__heap_size__) ? __heap_size__ : 0x00000100;
STACK_SIZE = DEFINED(__stack_size__) ? __stack_size__ : 0x00000100;
/* Specify the memory areas */
MEMORY
{
m_interrupts          (RX) : ORIGIN = 0x00000000, LENGTH = 0x00000100
m_flash_config        (RX) : ORIGIN = 0x00000400, LENGTH = 0x00000010
m_text                (RX) : ORIGIN = 0x00000410, LENGTH = 0x0000FBF0
m_data                (RW) : ORIGIN = 0x1FFFFC00, LENGTH = 0x00010000
}

And I have tried to change into something like this:

HEAP_SIZE = DEFINED(__heap_size__) ? __heap_size__ : 0x0000FFFF;
STACK_SIZE = DEFINED(__stack_size__) ? __stack_size__ : 0x00000200;
/* Specify the memory areas */
MEMORY
{
m_interrupts          (RX) : ORIGIN = 0x00000000, LENGTH = 0x00000100
m_flash_config        (RX) : ORIGIN = 0x00000400, LENGTH = 0x00000010
m_text                (RX) : ORIGIN = 0x00000410, LENGTH = 0x0000FBF0
m_data                (RW) : ORIGIN = 0x1FFFFC00, LENGTH = 0x0001FFFF

But with this configuration it won't work even with 10 samples/channel.

And the thing is that the project is also using functions like printf() which requires a pretty high amount of memory.

The question is: How do I increase memory to it's maximum limits?

Microcontroller used: Kinetis SKEAZN642

I have also attached the project in case it helps.

Re: Adc Sampling running out of memory?

mjbcswitzerland — Mon, 12 Nov 2018 14:09:10 GMT

Hi Alex

The KEA64 has maximum 4k SRAM so I think that you will need to use something like an IIR low pass filter (requiring only a couple of bytes of storage per channel) to do the averaging rather than long buffers in RAM (which would avoid you needing to solve the RAM setup too).

Regards

Mark

topic Adc Sampling running out of memory? in Kinetis Microcontrollers

Adc Sampling running out of memory?

Re: Adc Sampling running out of memory?