I have CH344Q, GPIO1 (OUT pin) connected to pull down 10K resistor.

The GPIO functional normal, but first time that I connect the board to power I have positive pulse of some ms.

How can I disable the first unwanted pulse ?

Hello，What is the purpose of adding a 10K pull-down resistor? Is it to make RTS0 (GPO1) default to a low level after power on.

Hi,

Yes, we need "0" at power up, so I add PD 10K for sure that there will no any noise.

Hi

Any fedback for us ? 

How can we disable the first unwanted pulse when chip get the power ?

Hello，

Reply to the question in the email:

Problem 1: Opening the serial port will cause the RTS and DTR to slow down for several tens of microseconds. You can disable modemhandshake function, as shown in the following figure.

Problem 2: When opening the serial port to send data, there will be many unwanted pulses. Please confirm whether the DTR pin is switched to TNOW function. If it is DTR function, you can send data at intervals and use an oscilloscope to observe whether the DTR unwanted pulses is normal during the period of no data transmission, in order to rule out whether the DTR unwanted pulses fluctuation is caused by TXD signal interference.