A detection method of automobile switch signal

Abstract

A method for detecting a switch signal of an automobile, comprising: step 1: establishing a detection circuit; step 2: connecting the detection circuit to the CPU: the negative end of the diode D1 is used as an input terminal to receive the switch signal INPUT of the automobile; the transistor Q1 The collector of the transistor Q2 is connected to the IO port of the CPU to input the TTL level signal OUTPUT to the CPU; the base of the triode Q2 is connected to the IO port of the CPU after connecting the resistor R6 in series to receive the timing scanning signal PULL_DOWN of the CPU; Step 3: The CPU generates Regularly scan the signal PULL_DOWN to control whether the INPUT at the input end is connected to the ground by the pull-down resistor R4, and read the value of the IO port every time a switch is made, and then compare it with the OUTPUT read last time: if the OUTPUT read twice is the same , then: CPU reads that OUTPUT is 1, then judges that INPUT is low level; reads OUTPUT is 0, then INPUT is high level; When OUTPUT is judged to be high level; when there is no pull-down resistor, judge OUTPUT to be low level.

Description

technical field [0001] The invention belongs to a state detection circuit, in particular to a detection circuit of an automobile switch signal. Background technique [0002] At present, there are three states in the switch signal detection on the car: high level (connected to the positive pole of the car battery), low level (grounded, connected to the negative pole of the battery), and floating, and there are two effective states: high active and low active. There are several traditional solutions for the switch signal detection of automobiles: using optocoupler isolation conversion, diode isolation conversion and AD acquisition, etc., and these traditional solutions can only be aimed at only one effective state (that is, a circuit can only be used alone) Detect high effective or low effective), and the IO of a CPU can only recognize two states, and it is impossible to achieve high effective or low effective and compatible solutions at the same time. Among them, the resista...

AI Technical Summary

Problems solved by technology

[0004] Although the scheme proposed by this patent can also be used in the detection circuit of the automotive switching signal, the detection circuit provided by it has no effective measures to protect it, and the resistance is directly introduced into the IO port of the CPU, which may damage the CPU, and the circuit structure is complicated. ,increase cost