McSPI of AM335x

Hiroyasu Tazawa1

Hi, Everyone

I have a quetion about McSPI of AM335x.

Our McSPI's clock is 40MHz.but We get ded time between TX byte and next byte.
This dead time is about 10us.
All time include TX time and dead time is about 800bps.

Do you know how to improve this ?
We think EDMA and McSPI turbo mode should be used.

and Can you tell me how much McSPI's Max throughput iclude dead time ?
We wanna know about case of McSPI's Max throughput after improve.

Best Regards
Hiroyasu

over 9 years ago

0 Yordan Kovachev over 9 years ago

TI__Guru**** 161600 points

Hi,

Which SDK do you use? Can you describe the use case in which you get this dead time, i.e. do you use spidev to transmit a byte, or do you use your customized application?

As you can see from am33xx.dtsi edma is used for SPI transactions:

spi0: spi@48030000 {
compatible = "ti,omap4-mcspi";
#address-cells = <1>;
#size-cells = <0>;
reg = <0x48030000 0x400>;
interrupts = <65>;
ti,spi-num-cs = <2>;
ti,hwmods = "spi0";
dmas = <&edma 16
&edma 17
&edma 18
&edma 19>;
dma-names = "tx0", "rx0", "tx1", "rx1";
status = "disabled";
};

As for the TURBO mode, currently it is enabled, when more than one word is transmitted on the spi channel. You could force it to improve the throughput of an spi channel by setting MCSPI_CHxCONF[19]TURBO bit.

Best Regards,
Yordan

0 Hiroyasu Tazawa1 over 9 years ago in reply to Yordan Kovachev

Guru 12350 points

Hi, Yordan

Thank you for your reply.

Our customer use Starterware base.
Do you know this case total throughput ?

Actually We wanna know about Device potential Max throughput
Do you know that ?

Best Regards
Hiroyasu

0 Hiroyasu Tazawa1 over 9 years ago in reply to Hiroyasu Tazawa1

Guru 12350 points

Hi Yordan

Sorry, previous first qustion means "Do you know How much total speed on this case you show ?"

Best regards
Hiroyasu

0 Biser Gatchev-XID over 9 years ago in reply to Hiroyasu Tazawa1

TI__Guru**** 393215 points

Please post Starterware questions in the Starterware forum: e2e.ti.com/.../790.aspx

0 Hiroyasu Tazawa1 over 9 years ago in reply to Biser Gatchev-XID

Guru 12350 points

Hi, Biser

We use Starterware. but I ask you about AM335x's device.

”Can you tell me how much McSPI's Max throughput iclude dead time ?”

Don't you know that ?

Best Regards
Hiroyasu

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McSPI of AM335x