Update DMA source buffer before software trigger

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Update DMA source buffer before software trigger

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r_poelstra
Contributor I

Hi,

I've configured a USART TX DMA channel (using the graphical config tool) that I trigger from software when bytes are available to be transmitted using:

DMA_DoChannelSoftwareTrigger(DMA0_DMA_BASEADDR, DMA0_LOG_UART_DMA_CHANNEL);

This works fine, but only with a fixed number of bytes each trigger.

How can I update the DMA channel so it knows how many bytes it should transfer?

 

Thanks in advance.

Kind regards,

 

Remco Poelstra

 

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Alice_Yang
NXP TechSupport
NXP TechSupport

Hello Remco Poelstra,

Yes, the DMA only can transfer fixed number of bits.

And a ring buffer DMA maybe suit for you , there is demo"lpcxpresso845max_usart_transfer_rb_dma" under SDK, you can have a look.

 

Regards,

Alice

 

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r_poelstra
Contributor I

Thanks for the reply.

I'll look into the ring buffer example. It might indeed be what I need.

 

Kind regards,

 

Remco Poelstra

 

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Alice_Yang
NXP TechSupport
NXP TechSupport

Hello Remco Poelstra,

Yes, the DMA only can transfer fixed number of bits.

And a ring buffer DMA maybe suit for you , there is demo"lpcxpresso845max_usart_transfer_rb_dma" under SDK, you can have a look.

 

Regards,

Alice

 

View solution in original post

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r_poelstra
Contributor I

Hi,

 

I'm using LPC844.

Kind regards,

 

Remco Poelstra

 

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ZhangJennie
NXP TechSupport
NXP TechSupport

Hi 

Please let us know your chip part number, thus we can assign right engineer for your issue.

Thanks,

Jun Zhang

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