MCU drives H-bridge circuit

    When I was chatting today, an idea suddenly popped up: the driving circuit of the remote control car is an H-bridge circuit, which should be driven by a single-chip microcomputer. If it can be driven, it can save a lot of trouble. In this way, the control loop only needs the minimum system of the single-chip microcomputer, plus the driving part of the original control loop.

        Just do it when you think of it. I just happen to have two circuit boards from remote control cars on hand. . Let's check the information first. One chip is RX-2, and the label of the other chip has been polished off. . It doesn't matter, anyway, most of the four-way controllers are RX-2 series. . . Refer to the information of RX-2 and confirm the chip pins. Then refer to RX-2 and judge that the other one is similar, and the output pins are the same. According to the information of RX-2, the current of the output pin is greater than 1mA. The microcontroller can achieve it.

        The wiring is that the four control wires are directly led out and soldered to the first four pins of P0 of the microcontroller. The power supply of the control board is directly soldered to the power supply of the microcontroller. In this way, I started to test with two motors.

        When the power is turned on, the power indicator of the MCU flashes. The system cannot run at all. After power off, the MCU is tested separately, and there is no problem. The control board is also tested separately, and there is no problem. There are two reasons for this: one is that the driving current of the MCU is too large, which interferes with the front transistor driven by the H bridge; the second is that all ports will have a power-on self-test when the MCU is started.

        The first question reconfirmed the parameters of 9014. The maximum base current can reach 100mA. The original driver circuit has a 10K resistor in series on the base of 9014. Therefore, it is judged that the base current will not exceed 100mA. The first speculation is ruled out.

        The second question is that when I was in contact with the microcontroller, I remember reading on http://www.51hei.com that when the microcontroller starts the self-test, all the output pins will have a high potential. In this case, when the four transistors of the H bridge are energized at the same time, they will all be turned on, which is equivalent to a short circuit. The power supply I used was modified from a 5V mobile phone charger. When there is an overcurrent, it will be powered off for protection. Because the driver board and the microcontroller share a power supply. After the power supply is cut off due to a short circuit, the microcontroller will be powered off. When the power supply is restored, the microcontroller self-checks and then short-circuits again. In this way, the power indicator light will flash. The solution is to add a power supply again, power the microcontroller and the driver board separately, and then connect the negative poles of the two power supplies. In this way, the debugging is successful. The motor can start and stop as required. . . The disadvantage of this method is that it cannot be operated with a single power supply. I don’t know if it will cause a short circuit when driven by a battery, causing the voltage to be too low, causing the microcontroller to fail to operate. . .

    Does anyone have a better solution? Adding resistors seems to consume a lot of power. I need to find a way to avoid the microcontroller's startup self-test.
Attached are photos, hehe