µTasker Forum

µTasker Forum => NXP^TM M522XX, KINETIS and i.MX RT => Topic started by: tr111 on November 14, 2007, 10:30:12 AM

Title: how to set the Bit rate of 52235evb'CAN?
Post by: tr111 on November 14, 2007, 10:30:12 AM

I can't understand that :
 switch (pars->ulSpeed) {                                             // M5223X EVB
    case 1000000:
        CANCTRL = ((3 << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME2 | PHASE_BUF_SEG1_LEN3 | PHASE_BUF_SEG2_LEN2); // Initialise the CAN controller with the required speed and parameters
        break;

    default:                                                             // 40 KHz
        CANCTRL = ((24 << 24) | RJW_2 | EXTAL_CLK_SOURCE | PROPSEG_BIT_TIME8 | PHASE_BUF_SEG1_LEN8 | PHASE_BUF_SEG2_LEN8); // Initialise the CAN controller with the required speed and parameters
        break;

    }
BUT I want to get the 100 khz,how can I get???

Title: Re: how to set the Bit rate of 52235evb'CAN?
Post by: mark on November 14, 2007, 01:15:13 PM

Hi

The calculation of the bit times is not that easy and so there are two values in the driver:

- a slow one which can be useful if the bus seems to be unreliable (assuming that slower speeds are more likely to work even when there is a problem with the connection). 40kHz was chosen.

- the 'normal' speed which most people use - 1MHz.

If you need a different frequency you can add a set using a new case statement with the speed you need. It is best to carefully calculate the set up of the speed (it is not really possible to calculate it from a formular since there are various times which need to be set to suit it. This is a bit imperical.)

Regards

Mark