topic Re: Maximum SPI Clock (output) speed LPC54S018 EVK in LPC Microcontrollers

Maximum SPI Clock (output) speed LPC54S018 EVK

jainilshah — Mon, 21 Feb 2022 18:17:15 GMT

Hi,

I am working with LPC54S018 EVK and want to generate maximum SPI clock frequency. Below are my observations:-

1. Getting 12MHz clock inspite of attaching HF clock (kFRO_HF_to_FLEXCOMM9). No effect of increased baud rate. (All the SPI pins are connected)

2. Getting 48MHz clock when kFRO_HF_to_FLEXCOMM9 is used and baud rate is set to 48MHz. In this case, only SCLK is connected, other SPI pins are not connected.

Let me know how can I generate maximum SPI clock o/p frequency? Can I use FLEXCOMM0-9 to generate maximum SPI clock o/p? (FLEXCOMM10 is not available on EVK)

Also suggest what changes are required to generate max SPI clock o/p frequency?

Re: Maximum SPI Clock (output) speed LPC54S018 EVK

xiangjun_rong — Tue, 22 Feb 2022 05:32:50 GMT

Hi,

Regarding the maximum SPI clock frequency of LPC54S018, pls refer to the data sheet of LPC54S018, the master mode, the SPI baud rate is 48M bit/s, in slave mode, the baud rate is 14M bit/s.

Assume that you want to get 48MHz for SCK signal, If you use the code kFRO_HF_to_FLEXCOMM9, the SPI drivig clock will be 48MHz.

and you have to set up the SPI baud rate by writing the SPI divider regisyter as 0, the SPI_SCK clock frequency will be 48MHz.

Hope it can help you

Re: Maximum SPI Clock (output) speed LPC54S018 EVK

jainilshah — Tue, 22 Feb 2022 17:01:38 GMT

Thanks.

Re: Maximum SPI Clock (output) speed LPC54S018 EVK

jainilshah — Tue, 22 Feb 2022 17:19:00 GMT

Please review my code changes as below. I have done modification in spi_dma_transfer demo app available inside SDK.

1. Added these lines.

/* attach 12 MHz clock to SPI2 */
CLOCK_AttachClk(kFRO_HF_to_FLEXCOMM2);

/* attach 12 MHz clock to SPI9 */
CLOCK_AttachClk(kFRO_HF_to_FLEXCOMM9);

2. Added this line.

masterConfig.baudRate_Bps = 48000000U;

Let me know in case anything is missing here.