Key scanning circuit of mobile communication terminal

Abstract

The present invention relates to the key scanning circuit of mobile communication terminal, is made up of following several parts: the keypad that is made up of the key that is connected together in parallel; Trigger button and terminate the event trigger of button event; Store the state register ( Register); carry out the I2C communication part of the I2C communication with the mobile base station modem (MSM) chip; if a button event occurs, read the value currently pressed by the interface part and store it in the above-mentioned register, and carry out the I2C communication part and the MSM chip through the above-mentioned I2C communication part Communication, and send the key value stored in the above register to the main controller of the MSM chip. The invention overcomes the defects of the known technology. Since the I2C mode is used to perform key scanning, the keys can be quickly identified through a simple algorithm, and noises during key scanning can be eliminated at the same time.

Description

technical field [0001] The present invention relates to a mobile communication terminal, in particular to a key scanning circuit (KEY SCANNING CIRCUIT FOR MOBILE COMMUNICATION TERMINAL) for a mobile communication terminal that uses I2C to perform key scanning and can eliminate noise during key scanning. Background technique [0002] Typically, keypads are organized in a matrix structure. [0003] figure 1 It is a schematic diagram of a keypad with a 5*5 matrix structure. [0004] The known keypad structure with a matrix structure is that a plurality of row (row) lines and a plurality of vertical (column) lines intersecting positions connected to a plurality of key scanning ports of the controller (not shown), are connected with various key, and detect the corresponding key event. [0005] The keypad of the matrix structure adopts a polling method to identify keys, and the controller (not shown) outputs polling signals to the vertical lines of the keypad sequentially with ...

AI Technical Summary

Problems solved by technology

[0007] However, due to the large number of buttons on the original keypad, the mobile base station modem chip (MObile Station Modem, MSM chip) needs a lot of GPIO (General Purpose Input Output) pins, so the circuit is relatively large, which brings a lot of problems to the miniaturization of the terminal. Difficulty

[0008] Furthermore, since the original key scanning adopts the polling method, there will be high-frequency (RF) noise, which will affect the work of the terminal.

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