#define LOS_ERRNO_SWTMR_MAXSIZE   LOS_ERRNO_OS_ERROR(LOS_MOD_SWTMR, 0x04)

Software timer error code: The number of software timers exceeds the configured permitted maximum number.

Value: 0x02000304

Solution: Re-configure the permitted maximum number of software timers, or wait for a software timer to become available.

在文件los_swtmr.h100行定义。