AM335X-EVM UART

sumanth g

Intellectual 305 points

How to access UART through DMA (direct memory access)

over 10 years ago

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

What software are you using?

0 sumanth g over 10 years ago in reply to Biser Gatchev-XID

Intellectual 305 points

linux kernel:4.1
uboot: 2015

0 sumanth g over 10 years ago

Intellectual 305 points

1.How to access DMA in am335x-evm board

my requirement is:

I want to receive the Data continuously from the function generator like sine wave or square wave with some amplitude and frequency is given to the uart0. Here i want to use the DMA to store the data like buffer and i want to transmit the data from the DMA to receiver output.

2.How can i initialize the DMA to store the data and transmit the data which has been received.

0 Biser Gatchev-XID over 10 years ago

TI__Guru**** 393215 points

You already have an identical thread opened. This will be attached to your existing thread. Please do not open multiple threads on the same topic in this forum.

0 sumanth g over 10 years ago in reply to Biser Gatchev-XID

Intellectual 305 points

Hi Biser,
u didn't give the reply for the post.

0 Yordan Kovachev over 10 years ago in reply to sumanth g

TI__Guru**** 161600 points

Hi,

Kernel 4.1 uses omap_8250.c driver. In order to initialize the dma, you need to add the following lines of code in uartX node in am33xx.dtsi:
dmas = <&edma Z>, <&edma K>;
dma-names = "tx", "rx";
Where Z & K are the dma channels you want to use.

If you have a look in omap_8350.c you'll see that you also need to add: CONFIG_SERIAL_8250_DMA=y in tisdk_am335x-evm_defconfig.

In fact, if you haven't changed the kernel source, all these configurations should be present.

Best Regards,
Yordan

0 sumanth g over 10 years ago in reply to Yordan Kovachev

Intellectual 305 points

Hi Yordan,
By using abow cmds in dtsi. it will initialize the DMA. But can u tell me about DMA user application program. So it can record the data continually and store the data and transmit the data using DMA.

0 Yordan Kovachev over 10 years ago in reply to sumanth g

TI__Guru**** 161600 points

Hi,

This is use-case specific.

The guides, I can think of, are:
linux kernel documentation: Documentation/dmaengine/
AM335x GEL Files: processors.wiki.ti.com/.../OMAP_and_Sitara_CCS_support
Processor SDK Linux DMA wiki: processors.wiki.ti.com/.../Processor_SDK_Linux_DMA

But you'll need to adapt the information from the above link to fit your needs.

Hope this helps.

Best Regards,
Yordan

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AM335X-EVM UART