LPC4357 GP_CLKIN input singal frequence monitor

[skysky]

i want to use the LPC4357's GP_CLKIN fun--use pin-PF_4 as GP_CLKIN,the singal is Sin-Wave,the frequence is about 17MHZ. I use the Frequency monitor register,but i can not read the input singal frequence.

the code such as :

the PF_4 pin set as gp_clkin:

LPC_SCU->SFSPF_4 = (0 << 7) | (0 << 6) | (1 << 5) | (2 << 3) | 1; //GP_CLKIN

loop read some times,as follow:

for(i=0; i<FRE_NUM; i++)
{
fre[i] = freq_measure(4); //GP_CLKIN

for(j=0; j<10000; j++);
}

and then, function freq_measure(),as follow:

uint32_t freq_measure(uint32_t clk_sel)
{
volatile uint32_t fcnt, rcnt, fout;

/* Set register values */
LPC_CGU->FREQ_MON &= ~(1 << 23); /* Stop frequency counters */
LPC_CGU->FREQ_MON = (clk_sel << 24) | IRC_CNT; /* RCNT == 511 */
LPC_CGU->FREQ_MON |= (1 << 23); /* Start RCNT and FCNT */

while(LPC_CGU->FREQ_MON & (1 << 23))
{
fcnt = (LPC_CGU->FREQ_MON >> 9) & 0x3FFF;
rcnt = (LPC_CGU->FREQ_MON ) & 0x01FF;
if(fcnt == 0 && rcnt == 0)
{
return (0); /* No input clock present */
}
}

fcnt = (LPC_CGU->FREQ_MON >> 9) & 0x3FFF;
fout = fcnt * (12000000U/IRC_CNT); /* FCNT * (IRC_CLK / RCNT) */

return (fout);
}

when i debug,after the measure started,FREQ_MON's MEAS bit don't clear,and fcnt=0 always,but rcnt don't be 0.

the program is loop in the  while(LPC_CGU->FREQ_MON & (1 << 23))

So,is ther some initial error?

[jeremyzhou]

Hi sky sky ,

Thank you for your interest in NXP Semiconductor products and 

the opportunity to serve you.

Pleas try the the following CGU_FrequencyMonitor function.

Hope this can help.

/*********************************************************************//**
 * @brief          Compare one source clock to IRC clock
 * @param[in]     Clock     Clock entity that will be compared to IRC, should be:
 *                          - CGU_CLKSRC_32KHZ_OSC          :32Khz crystal oscillator
 *                          - CGU_CLKSRC_ENET_RX_CLK     :Ethernet receive clock
 *                          - CGU_CLKSRC_ENET_TX_CLK     :Ethernet transmit clock
 *                          - CGU_CLKSRC_GP_CLKIN          :General purpose input clock
 *                          - CGU_CLKSRC_XTAL_OSC          :Crystal oscillator
 *                          - CGU_CLKSRC_PLL0               :PLL0 clock
 *                          - CGU_CLKSRC_PLL1               :PLL1 clock
 *                          - CGU_CLKSRC_IDIVA               :Integer divider register A
 *                          - CGU_CLKSRC_IDIVB               :Integer divider register B
 *                          - CGU_CLKSRC_IDIVC               :Integer divider register C
 *                          - CGU_CLKSRC_IDIVD               :Integer divider register D
 *                          - CGU_CLKSRC_IDIVE               :Integer divider register E
 *                          - CGU_BASE_SAFE                    :Base safe clock (always on)for WDT
 *                          - CGU_BASE_USB0                    :Base clock for USB0
 *                          - CGU_BASE_USB1                    :Base clock for USB1
 *                          - CGU_BASE_M4                    :System base clock for ARM Cortex-M3 core
 *                                                              and APB peripheral blocks #0 and #2
 *                          - CGU_BASE_SPIFI               :Base clock for SPIFI
 *                          - CGU_BASE_PHY_RX               :Base clock for Ethernet PHY Rx
 *                          - CGU_BASE_PHY_TX               :Base clock for Ethernet PHY Tx
 *                          - CGU_BASE_APB1                    :Base clock for APB peripheral block #1
 *                          - CGU_BASE_APB3                    :Base clock for APB peripheral block #3
 *                          - CGU_BASE_LCD                    :Base clock for LCD
 *                          - CGU_BASE_SDIO                    :Base clock for SDIO card reader
 *                          - CGU_BASE_SSP0                    :Base clock for SSP0
 *                          - CGU_BASE_SSP1                    :Base clock for SSP1
 *                          - CGU_BASE_UART0               :Base clock for UART0
 *                          - CGU_BASE_UART1               :Base clock for UART1
 *                          - CGU_BASE_UART2               :Base clock for UART2
 *                          - CGU_BASE_UART3               :Base clock for UART3
 *                          - CGU_BASE_CLKOUT               :Base clock for CLKOUT pin
 * @param[in]     m     Multiple value pointer
 * @param[in]     d     Divider value pointer
 * @return           Compare status, could be:
 *                          - (-1): fail
 *                          - 0: successful
 * @note          Formula used to compare:
 *                     FClock = F_IRC* m / d
 **********************************************************************/
int CGU_FrequencyMonitor(CGU_ENTITY_T Clock, uint32_t *m, uint32_t *d){
     uint32_t n,c,temp;
     int i;

     /* Maximum allow RCOUNT number */
     c= 511;
     /* Check Source Clock Freq is larger or smaller */
     LPC_CGU->FREQ_MON = (Clock<<24) | 1<<23 | c;
     while(LPC_CGU->FREQ_MON & (1 <<23));
     for(i=0;i<10000;i++);
     temp = (LPC_CGU->FREQ_MON >>9) & 0x3FFF;

     if(temp == 0) /* too low F < 12000000/511*/
          return -1;
     if(temp > 511){ /* larger */

          c = 511 - (LPC_CGU->FREQ_MON&0x1FF);
     }else{
          do{
               c--;
               LPC_CGU->FREQ_MON = (Clock<<24) | 1<<23 | c;
               while(LPC_CGU->FREQ_MON & (1 <<23));
               for(i=0;i<10000;i++);
               n = (LPC_CGU->FREQ_MON >>9) & 0x3FFF;
          }while(n==temp);
          c++;
     }
     *m = temp;
     *d = c;
     return 0;
}‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

TIC

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[skysky]

hi jeremy:

你给的这个频率监测的代码，好像有些问题哦。

我实际测试的话，只能测出小于12M的信号频率，大于12M的信号频率都是有些错误的。

比如，16-7M的信号测出来只有6，700K.

更大一点的，32M左右的信号，测出来只有4M多一点

不知道是函数处理里面哪里有点不对

[skysky]

Dear Jeremy:

   In view of this problem,now,i have found another issue.

i use two board have the same program that you reply,one is correct,another is error.

The error is wait always at 

 LPC_CGU->FREQ_MON = (Clock<<24) | 1<<23 | c;
     while(LPC_CGU->FREQ_MON & (1 <<23));

According to the instructions on the document 《13.6.1 Frequency monitor register》，when the RCNT counts down towards 0,the MEAS bit will be 0,but why 

while(LPC_CGU->FREQ_MON & (1 <<23));

can not complete??

the error board also works correct yesterday.

So,where is the bug? i think about the PF_4 pin or FREQ_MON register has error?

[skysky]

hi jeremy:

i found out the problem is at the pin PF_4. When i connect the external signal to the PF_4,the singal is pulled down a low level,and disconnect the pin,the singal recover normal.

So it isn't a software problem.

It seems too complex to used for measuring high frequence singal.

 Especially the code such as for(i=0; i<10000; i++);

Is it necessary？

[jeremyzhou]

Hi sky sky,

Thanks for you reply.

I think the phenomenal is normal, this phenomenal is also exist in the external oscillator.

Hope this is clear.
Have a great day,
TIC

-----------------------------------------------------------------------------------------------------------------------
Note: If this post answers your question, please click the Correct Answer button. Thank you!
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[skysky]

hi jeremy:

  thank you for your reply.

i will try the code you provide.