BSP setting for USB

[Teckna]

Hi everyone,

I'm working on a custom board with CW10, MQX 3.8 and K60N512 processor.

With this board I have successfully worked with MQX 3.7. Now that I ported all custom drivers to MQX 3.8, everything is ok except the USB. I cloned the BSP twrk60n512 and I modified the line 58 in the bsp_cm.h file from

#define CPU_XTAL_CLK_HZ                 0x02FAF080U /* Value of the external crystal or oscillator clock frequency in Hz */

to

#define CPU_XTAL_CLK_HZ                 0x016E3600U /* Value of the external crystal or oscillator clock frequency in Hz */

(my external clock is 24 MHz instead of 50 MHz as in the twrk60n512 board)

When I insert the USB cable in the PC port the device is not recognized, even if leave the 50 MHz define.

The only way I found to make the USB work is to set the SIM_CLKDIV2.USBDIV field to 0 instead of 1 in the Cpu_SetClockConfiguration function: I modified the line 717 in the bsp_cm.c file from

      SIM_CLKDIV2 = (uint32_t)((SIM_CLKDIV2 & (uint32_t)~0x0DUL) | (uint32_t)0x02UL); /* Update USB clock prescalers */

to

      SIM_CLKDIV2 = (uint32_t)(SIM_CLKDIV2 & (uint32_t)~0x0FUL); /* Update USB clock prescalers */

Am I right or do I have to modifiy other things?

Any other advice?

Many thanks

Teckna

[petr_uhlir]

The easiest way for you when you are using CodeWarrior would be to setup your clock settings using Processor Expert. 

You can follow descriprion in "...Freescale MQX 3.8\doc\tools\cw\Howto_SetupKinetisClock_UsingPE.pdf"

[Mohsin455]

Hi,

The USB requires 48MHz clock. Hence you need to  USBFRAC=1 and USBDIV=0.

Regards,

Mohsin

[Teckna · Accepted solution]

Solved:

I need USBFRAC=0 and USBDIV=1 as for twrk60n512 bsp, but i need to modifiy the values written in the MCG_C5.PRDIV field in the bsp_cm.c file (fclk = 50 MHz => PRDIV = 0x18 resulting in 2 MHz in twrk60n512 bsp, fclk = 24 MHz => PRDIV = 0x0B resulting in same 2 MHz in my custom bsp).

In MQX 3.7 this value was set depending on the macro value representing external clock frequency, in MQX is written directly in the code: why this mechanism has been depreceted, while it is so useful?

Many thanks

Teckna

[egoodii]

Agreed -- Embedding this Processor Expert-generated code into an OS release is 'not friendly', especially with all the embedded hard-constants, for ANY user not tied-in with their CodeWarrior toolset.