Calibration method and device for system clock of USB equipment

Abstract

The invention discloses a calibration method and device for a system clock of USB equipment. The method comprises the following steps: taking the system clock of the USB equipment as a clock source of a USB equipment timer in counting function after performing frequency division to the system clock of the USB equipment through utilizing the counting function and capturing function of the USB equipment timer, and taking a low-velocity clock of the USB equipment as a trigger source of the USB equipment timer in capturing function; capturing the jump edge of the trigger source, and obtaining the actual count value of the system clock of a corresponding capturing interval; calibrating the frequency of the system clock of the USB equipment as per the obtained actual count value, a preset theoretic count value and an acceptable error range. According to the invention, the calibration method and device have the benefit that the frequency of the system clock can be calibrated in time when the USB equipment system clock has deviation in frequency, so that the USB equipment can be normally used; further, the cost of the USB equipment is reduced as only an HSI crystal oscillator is adopted by the USB equipment.

Description

technical field [0001] The invention relates to USB technology, in particular to a method and device for calibrating a system clock of a USB device. Background technique [0002] The engine clock of the USB (Universal Serial Bus, Universal Serial Bus) device comes from the frequency division of the system clock, and the system clock comes from HSE (High speed external clock signal, high-speed external clock signal) or HSI (High speed internal clock signal, high-speed internal clock signal). The system clock generated by the USB device using the HSE crystal oscillator does not need to be calibrated, but this solution requires the addition of an HSE crystal oscillator, which increases the size and space of the PCB (Printed Circuit Board, printed circuit board) in the USB device, and also increases the cost of the USB device; For USB devices that directly use the HSI crystal oscillator, the USB device can work normally at room temperature, but in harsh environments, because th...

AI Technical Summary

Problems solved by technology

The system clock generated by the USB device using the HSE crystal oscillator does not need to be calibrated, but this solution requires the addition of an HSE crystal oscillator, which increases the size and space of the PCB (Printed Circuit Board, printed circuit board) in the USB device, and also increases the cost of the USB device; For USB devices that directly use the HSI crystal oscillator, the USB device can work normally at room temperatu...

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