SSP1 Clock on LPC18xx is continuous

[gvk51]

Hi All,

I am working to interface uSD card using SSP1 controller of LPC1837 (In built SD controller is fixed for some other functionality).

SSP1 controller is configured in master SPI mode with CPOL & CPOH as 0. I have seen the clock is coming continuously just after initialising the SSP1 module without even starting the actual transfer of the data. This is not expected behaviour, please give your inputs If I am missing anything during configuration. 

Thanks.

#ssp1‌ #master spi‌ #lpc18xx‌

[ionutalexa · Accepted solution]

Hi,

I am seeing the same behavior on our LPC1857. The main issue is that in production, the SDcards become useless. 

We need a fix for this as the customers complain.

Kind regards,

Ionut Alexa

[gvk51]

Hi lonut Alexa,

Thanks for your response in clarifying.

[gvk51]

Carlos Mendoza,

Thanks for your response.

Following my setup details

• LPCXpress IDE
• lpcopen_3_01_lpcxpresso_nxp_lpcxpresso_1837 example source
• IKALogic analyzer capture CLK, MISO, MOIS @1Mz (also used 5 & 10MHz sampling), Signals probed are shown below
  
• Working on LPC183x-Xplorer board.

I have shorted MISO line to MOSI line that is pin 5, 6 of J8 are shorted.

I have probed signal on logic change of the clock line, I see peculiar behavior of clock, Please give your comments

CLK is red line

Following is the serial console output, it shows transfer is passed as the MOSI & MISO are proper, but clock is not as expected/

Please give your comments why I am seeing the clock with 50% duty cycle?

I see clock is coming even though there is no data transmission. In the below scenario I have transmitted 6bytes, but the clock is keep on ticking??

Please give your inputs.

Thanks & Regards,

Vamshi G.

[Carlos_Mendoza]

Hi Vamshi,

I would recommend you to compare your configuration with the one from the periph_ssp example from th eLPCOpen package, the example describes how to use SSP in POLLING, INTERRUPT or DMA mode:

LPCOpen Software for LPC18XX|NXP 

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer