Actions
Forum Thread Details
  • State Verified Answer
  • Replies 5 replies
  • Subscribers 330 subscribers
  • Views 2466 views
  • Users 0 members are here
Related

PS SPI frequency

Former Member

Hello guys,
I have been working on zedboard since past few months.
I have a doubt regarding the SPI frequency and baud rate. As mentioned in the section B.30 of zynq 7000 Technical reference manual, there are 7 baud rate divisors.
My doubt is how to achieve any desired frequency ?
I have my spi code, i ran the code onto zynq ps section.
I connected oscilloscope to SCLK and ground and found out that the frequency was something 300khz, which seemed to be very incorrect(baud rate divisor was 4) as the clock frequency for SPI master has to be in the range 0 to 50Khz.
Can anybody tell how to precisely obtain any frequency and how to cross verify it whether it is correct or not ?
Is there any process to set frequency except the baud rate thing ?
Kindly suggest me over this.
Thanks.

Parents
  • 0

    Hello,

     

    Not sure what you mean by 'baud rate'.

     

    The SPI clock input is set in the Zynq Processing System hardware. If you open your Zynq Processing System IP in your block diagram and click on 'Clock Configuration' and expand 'IO Peripheral Clocks' you should see the SPI clock. The default is 166.66 MHz. You can leave that as the default (It must be at least 111 MHz).

     

    Then, in your SPI driver code, you can set the clock divider. If you look in the xspips example code you will see a call to a function XSpiPS_SetClkPrescaler. You can set the divisor for the 166.66 MHz input clock there. So, using the definition XSPIPS_CLK_PRESCALE_256 , will get you an SPI clock of around 651 KHz as an example.

     

    -Gary

  • 0 in reply to Former Member

    Hello,

     

    I am using Microzed board Zynq7020. when I checked My PS frequency for SPI is 166.66MHz. Then as you said I checked XSPIPS.h file but I am not able to find XSPIPS_CLK_PRESCALE function. Can you please tell me what am I missing? 

     

    Thank you

Reply Children
No Data