topic Re: DMA and PIT for FRDM K64F board in Kinetis Microcontrollers

DMA and PIT for FRDM K64F board

kirantujare — Tue, 03 May 2016 14:45:46 GMT

I'm working on a project where I'm trying to design a frequency generator. I want to use DMA and PIT(Periodic Interrupt Timer) feature on FRDM K64F board. I would like some help on the use of these on FRDM K64F board using KSDK+PE. I am using KDS Version: 3.2.0 and KSDK 1.3.

Re: DMA and PIT for FRDM K64F board

mario_castaneda — Wed, 04 May 2016 17:40:29 GMT

Hi Kiran

The next KDS 1.3 examples will help you to understand the configuration of the different modules that you want to use, DMA and PIT after that, you can modify your project on PE.

In the next path you can find the examples of the modules

C:\Freescale\KSDK_1.3.0\examples\frdmk64f\driver_examples\edma

C:\Freescale\KSDK_1.3.0\examples\frdmk64f\driver_examples\pit

The next example shows the configuration of PIT and DMA, saving the information that is taken of ADC channel

https://community.freescale.com/docs/DOC-102951

Hope it helps

Best Regards

Mario Castañeda

Re: DMA and PIT for FRDM K64F board

kirantujare — Wed, 04 May 2016 18:29:37 GMT

Thank you Mario!

I tried using DMA for a simple Sine wave and I got the correct output. However, I have to output 3 different waves for my project. I would like to know how I could make that work? Also, I want to use values from main.c file to trigger DMA in events.c file. How can I make that happen? Please let me know if you can provide any help whatsoever. I tried using "extern int q[50]" to access variable from main.c to events.c but it throws an error saying- " undefined reference to q"

Re: DMA and PIT for FRDM K64F board

mario_castaneda — Wed, 04 May 2016 20:28:06 GMT

Kiran

If you want to use variable from main.c to other source files, you should declare this variable as global in main.c for example: int q[50] = {0}; and this same variable needs to be included as extern in the other source file, for example, it will look like extern int q[50]; in events.c

How are you getting the sin values?

I am supposing you are moving data from internal buffers by using PIT to trigger dma channel, aren't you? If so, you will need to use other 2 dma channels as well as 2 PIT channels to replicate this behavior for other 2 signals and this way, all channels will be independently (frequency and data) for each signal

If you have another question let me now

Mario Castañeda

Re: DMA and PIT for FRDM K64F board

kirantujare — Thu, 05 May 2016 12:15:31 GMT

Thank you so much. It makes total sense now. I did like you said. But how do you check the output for the other two waveform. I am using DAC0_OUT(Analog Out) Pin to check the waveform on scope and I see only one waveform. Which pins will be used to check multiple outputs.?

Re: DMA and PIT for FRDM K64F board

kirantujare — Thu, 05 May 2016 12:58:49 GMT

If I use extern int q[7200]; in events .c after putting int q[7200] = {0} in main.c I get the error "undefined reference to 'q' " and if I use extern int q[7200] = {0} in events.c after putting int q[7200] = {0} in main.c I get a warning " 'q' initialized and declared 'extern' " Is this warning fine? I have attached the screenshots for the errors and warnings.

Re: DMA and PIT for FRDM K64F board

BlackNight — Thu, 05 May 2016 13:25:04 GMT

Hi Kiran,

Looks like you are struggling with basic C programming here, and the compiler is correct to flag what you did.

Using 'extern' is a *declaration*, i.e. it makes the symbol known to the compiler.

use something like

extern int q[7200];

is fine.

It is *not* ok in C to initialize a declaration like you did with

extern int q[7200] = {0};

as you mix up a declaration and a definition:

- declaration: makes the type/name of the variable known to the program

- definition: defines and allocates the memory for the variable.

So you should use

extern int q[7200];

for example in the header file.

And in a C file (only there) you make the definition of it with

int q[7200] = {0};

and as this is the definition, you can initialize it.

So one message from the compiler is that you should not initialize a declaration, the other message is that you only had a declaration, but no definition.

I hope this makes sense,

Erich

Re: DMA and PIT for FRDM K64F board

kirantujare — Thu, 05 May 2016 13:31:44 GMT

Hi Erich,
Thank you for the explanation.
I tried doing what you said as you can see the error in the screenshot 1 in the previous message. What could be the reason for it? I tried using extern int q[7200] in events.c as well as events.h file differently and I still get the error "undefined reference to 'q ' "

Re: DMA and PIT for FRDM K64F board

BlackNight — Thu, 05 May 2016 13:36:46 GMT

Use

extern int q[7200];

in events.h

and

int q[7200] = {0};

in events.c

Erich

Re: DMA and PIT for FRDM K64F board

kirantujare — Thu, 05 May 2016 13:52:32 GMT

Thank you so much Erich! It helped a lot. It is working now.
I want to output 3 waveforms from DAC. Is it possible to do that?
I am using DAC0_OUT(Analog Out) Pin to check the waveform on scope and I see only one waveform. Which pins will be used to check multiple outputs.? Is there an alternative way to do that. I am an amateur. This is my first project. Please bear with me if I sound silly.
Please let me know

Re: DMA and PIT for FRDM K64F board

mario_castaneda — Thu, 05 May 2016 20:37:27 GMT

If you want to see the 3 output waves at the same time is not possible. The FRDM K64F the package 100 LQFP only has 1 DAC module.

But if you want to get the different signals, you only have to do is select different channel for the 3 output waves depending the mux channel

Hope it helps

Best Regards

Mario Castañeda

Re: DMA and PIT for FRDM K64F board

kirantujare — Thu, 05 May 2016 21:07:43 GMT

Thank you for the reply. Currently, I am using DAC + PIT on Processor Expert. I have no idea how to select DMA Channels. I also could not figure out how to get DMA working for KSDK+PE project. I am sending calculated values from user input to DAC using an array. I am not sure if the approach is correct.

Re: DMA and PIT for FRDM K64F board

kirantujare — Fri, 06 May 2016 16:51:56 GMT

Can we generate a wave using values generated from a user given input without putting constant values in a buffer??

For example to generate sin wave: I have used the following piece of code:

#define DAC_TEST_BUFF_SIZE (120U)

uint16_t dac_buffer[DAC_TEST_BUFF_SIZE] =

{0x7ff, 0x86a, 0x8d5, 0x93f, 0x9a9, 0xa11, 0xa78, 0xadd, 0xb40, 0xba1,

0xbff, 0xc5a, 0xcb2, 0xd08, 0xd59, 0xda7, 0xdf1, 0xe36, 0xe77, 0xeb4,

0xeec, 0xf1f, 0xf4d, 0xf77, 0xf9a, 0xfb9, 0xfd2, 0xfe5, 0xff3, 0xffc,

0xfff, 0xffc, 0xff3, 0xfe5, 0xfd2, 0xfb9, 0xf9a, 0xf77, 0xf4d, 0xf1f,

0xeec, 0xeb4, 0xe77, 0xe36, 0xdf1, 0xda7, 0xd59, 0xd08, 0xcb2, 0xc5a,

0xbff, 0xba1, 0xb40, 0xadd, 0xa78, 0xa11, 0x9a9, 0x93f, 0x8d5, 0x86a,

0x7ff, 0x794, 0x729, 0x6bf, 0x655, 0x5ed, 0x586, 0x521, 0x4be, 0x45d,

0x3ff, 0x3a4, 0x34c, 0x2f6, 0x2a5, 0x257, 0x20d, 0x1c8, 0x187, 0x14a,

0x112, 0xdf, 0xb1, 0x87, 0x64, 0x45, 0x2c, 0x19, 0xb, 0x2,

0x0, 0x2, 0xb, 0x19, 0x2c, 0x45, 0x64, 0x87, 0xb1, 0xdf,

0x112, 0x14a, 0x187, 0x1c8, 0x20d, 0x257, 0x2a5, 0x2f6, 0x34c, 0x3a4,

0x3ff, 0x45d, 0x4be, 0x521, 0x586, 0x5ed, 0x655, 0x6bf, 0x729, 0x794};

uint16_t index = 0;

void pitTimer1_IRQHandler(void)

I want to generate a wave without using this lookup table. Is it possible to do that?
Does the buffer take constant values only?

Re: DMA and PIT for FRDM K64F board

mario_castaneda — Fri, 06 May 2016 16:54:09 GMT

Hi Kiran,

I took a look of the code and the signal, the PIT and DAC configuration are correct, but I recommend use different buffers for each signal, or make test with constant values and select one signal buffer to the DAC _out.

This example show you how to create the sine signal, using PIT + DAC. Some recommendations to calculate the data for the signal with constant values.

https://community.freescale.com/message/642235?et=watches.email.thread#comment-642235

Hope it Helps

Mario Castañeda

Re: DMA and PIT for FRDM K64F board

kirantujare — Sat, 07 May 2016 18:18:39 GMT

Thank you. I will try doing that and let you know how it goes.
The link redirects to the same page.

Re: DMA and PIT for FRDM K64F board

kirantujare — Mon, 09 May 2016 18:12:13 GMT

Thank you Mario. I got it all figured out. I am getting the output correctly. The only thing is I want to see it on two separate channels. Since I am using only using DMA+PIT, I don't know how to get the output on two separate channels. Still trying to figure out a way to do that.

Re: DMA and PIT for FRDM K64F board

kirantujare — Tue, 10 May 2016 20:55:18 GMT

Hi Mario,
I just found out that my 7200 data points get halved ( 3600) after sending them over to DAC.
Do you know why this would happen? I have attached the screenshot. After using this line of code the datapoints are halved

Re: DMA and PIT for FRDM K64F board

mario_castaneda — Wed, 11 May 2016 15:18:14 GMT

Hi Kiran

You could tried this way

for(index = 0 ; index z buffer_size ; index++)
    {
        DAC_DRV_Output(FSL_DACONV1,q[index]);
    }

If you have with the output, let me know

Mario

Re: DMA and PIT for FRDM K64F board

kirantujare — Wed, 11 May 2016 15:31:40 GMT

Hi Mario!

It does work. Thank you so much for your help :smileyhappy:

Re: DMA and PIT for FRDM K64F board

kirantujare — Wed, 11 May 2016 20:43:38 GMT

Hi Mario,

My code works perfectly and the output is shown on the oscilloscope. The only problem is that the data doesn't show continuously on the scope. I get the stream of ones and zeros(square wave) and then it flats out. I want the continuous flow of square wave. I get the expected wave after putting it in an infinite 'for' loop but the next line of code doesn't run. Please let me know if you have any suggestion/solution for it? I have the code below