topic Re: SPI burst in LPC Microcontrollers

SPI burst

venkatvallapane — Thu, 01 Jun 2017 18:01:44 GMT

Hi,

I am using LPC4330 Xplorer board and Invensense sensor.

The sensor requires back to back transactions (at least two) to complete register read/write operations.

First transaction is address with read/write indication and second transaction is data.

What I meant by back to back is CS should be de-asserted for 16 cycles.

When I fill SPI FIFO with two words (SPI is configured for word length as 8), I expected CS to be de-asserted for contentious 16 clocks but looks like its not.

When I set SPI word length as 16 and write one entry to SPI FIFO, I see transaction happening correctly to the sensor.

Please let me know how do I achieve burst transactions with SPI.

By the way, I am not using DMA mode.

Rgds,

Venkat.

Re: SPI burst

kerryzhou — Mon, 05 Jun 2017 06:15:52 GMT

Hello venkat vallapeneni,

There are two ways you can try:

1. configure the data size as 16bits in CR0[DSS]

2. You can configure the SSEL pin as the GPIO, then you GPIO to control de-assert, it will be more flexiable.

Wish it helps you!

If you still have question about it, please let me know!

Have a great day,
Kerry

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Re: SPI burst

venkatvallapane — Mon, 05 Jun 2017 08:13:22 GMT

Hi Kerry,

So there is no direct way to achieve CS being low as long as TX FIFO is not-empty using SPI?

For using option 1 (which I am already using), there is a problem. If I have to read/write more than one register supported as burst with address auto increment.

I will use GPIO option then.

Thanks.

Rgds,

Venkat.

Re: SPI burst

kerryzhou — Mon, 05 Jun 2017 08:54:08 GMT

Hello Venkat Vallapaneni,

You can try the GPIO option, it is more flexible to control.

Any further problem, just let me know!

Have a great day,
Kerry