TCAN4550: GPIO1 clockout function

Hi Emma,

The customer should only use a GPIO1_CONFIG value of "00" or "10"The GPIO1_CONFIG register values of 0x01 and 0x11 are Reserved and should not be used.  Some reserved register bits are simply unused, and others may be used for internal or development features that are not intended for use in a customer's application.

Emma Wang said:

So I have customer to comment this Init_CAN(void) code, then the issue disappeared, or it is harder to reproduced due to we did not test so long time.

do you have any ideas on why the bit is changed ?

The Init_CAN(void) function is the main function in the demo code that configures all of the TCAN4550's device settings.  I would think that if you commented out this entire function, then the device would not get configured or work at all.

The following line of code in the Init_CAN(void) function sets the GPIO1_CONFIG register value.

devConfig.GPIO1_CONFIG = TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG_GPO;      // GPIO set as GPO (Default)

This line is part of the devConfig settings shown below for reference.

	/* Configure the TCAN4550 Non-CAN-related functions */
	TCAN4x5x_DEV_CONFIG devConfig = {0};                        // Remember to initialize to 0, or you'll get random garbage!
	devConfig.SWE_DIS = 0;                                      // Keep Sleep Wake Error Enabled (it's a disable bit, not an enable)
	devConfig.DEVICE_RESET = 0;                                 // Not requesting a software reset
	devConfig.WD_EN = 0;                                        // Watchdog disabled
	devConfig.nWKRQ_CONFIG = 0;                                 // Mirror INH function (default)
	devConfig.INH_DIS = 0;                                      // INH enabled (default)
	devConfig.GPIO1_GPO_CONFIG = TCAN4x5x_DEV_CONFIG_GPO1_MCAN_INT1;    // MCAN nINT 1 (default)
	devConfig.FAIL_SAFE_EN = 0;                                 // Failsafe disabled (default)
	devConfig.GPIO1_CONFIG = TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG_GPO;      // GPIO set as GPO (Default)
	devConfig.WD_ACTION = TCAN4x5x_DEV_CONFIG_WDT_ACTION_nINT;  // Watchdog set an interrupt (default)
	devConfig.WD_BIT_RESET = 0;                                 // Don't reset the watchdog
	devConfig.nWKRQ_VOLTAGE = 0;                                // Set nWKRQ to internal voltage rail (default)
	devConfig.GPO2_CONFIG = TCAN4x5x_DEV_CONFIG_GPO2_NO_ACTION; // GPO2 has no behavior (default)
	devConfig.CLK_REF = 1;                                      // Input crystal is a 40 MHz crystal (default)
	devConfig.WAKE_CONFIG = TCAN4x5x_DEV_CONFIG_WAKE_BOTH_EDGES;// Wake pin can be triggered by either edge (default)
	TCAN4x5x_Device_Configure(&devConfig);                      // Configure the device with the above configuration

The TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG_GPO enum is included in the TCAN4x5x_Data_Structs.h file.  The code only offers the unreserved register settings as options.

typedef enum
{
    TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG_GPO = 0,
    TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG_WATCHDOG_INPUT = 2
} TCAN4x5x_DEV_CONFIG_GPIO1_CONFIG;

Can the customer verify their code is setting this register value to 0 (default) or 2 if they are using the watchdog feature?  It should not be set to 1 or 3 because those are reserved.

I don't know of any reason this bit's setting would change on it's own.  A noisy or poor quality SPI signal could cause SPI bits to get sampled incorrectly, but this would likely not be very repeatable and would corrupt other register values as well.

Regards,

Jonathan