A while ago I posted here about my GSM project using SIM900A where I accidentally designed it for 5V and had to fix it with a diode drop hack (thread link: [old thread]) — thanks again to everyone who helped me out there .

Now I’ve got another issue:
I have successfully installed the bootloader on my custom Arduino board using another arduino, but when I connect it to the PC via USB, it’s not showing up at all.

• I measured the voltage on the Arduino board: ~4.25 V
• I’m using the CH340C USB-to-UART IC (supply range 3.3–5 V)
• I already installed the CH340 drivers on my PC
• The TX pin blinks once when I press reset
• Voltage at CH340 pin is around 3.3 V

So right now the board is powering up, but the PC does not detect it at all, no COM port shows up.
i only connected the arduino for now. The Sim900 is not connected yet
Any help or suggestions would be really appreciated

 

Should the CH340 have a crystal between pins 7 and 8?

Like tins one.

 

Should the CH340 have a crystal between pins 7 and 8?
View attachment 354652
Like tins one.

The one i'm using is CH340C it has a built-in crystal oscillator.

 

I already installed the CH340 drivers on my PC

When you connect the board to the PC, does the CH340 appear in the device manager?

 

When you connect the board to the PC, does the CH340 appear in the device manager?
View attachment 354653

no nothing appears

 

So try to install these drivers https://cdn.sparkfun.com/assets/learn_tutorials/8/4/4/CH341SER.EXE
And see if this helps.

 

So try to install these drivers https://cdn.sparkfun.com/assets/learn_tutorials/8/4/4/CH341SER.EXE
And see if this helps.

i have installed it but nothing changes i think its a hardware problem but i cant figure out the reason

 

Did you click the "Uninstall" button first?
Disconnect the board from the PC.
Click on CH341SER.EXE and uninstall the drivers. Then click on the "Install" button.
After you finish, try to plug the board once again into the PC.

I forgot to ask about the windows. Is it 10 or 11?

 

when i click Uninstall it says No Device is found!
its not even says unknown device in Device Manager
i'm using windows 10 and i also tried it on linux system but no luck

 

when i click Uninstall it says No Device is found!

This means that you already uninstalled the drivers.
So now you need to install them. Here are the newest ones
https://www.wch-ic.com/downloads/CH341SER_ZIP.html

 

same

This means that you already uninstalled the drivers.
So now you need to install them. Here are the newest ones
https://www.wch-ic.com/downloads/CH341SER_ZIP.html

didn't work either

 

Last try. Download Zadig https://zadig.akeo.ie/
And see if Zadig can see CH340



You could also try to check the continuity (using a multimeter) between D+/D- of a USB port and the CH340C chip D+ and D- pins.
And the supply voltage across CH340.

 

thank you i have checked the d+ and d- and the usb type c was not soldered well after i solder it again it works

 

I'm glad that you managed to find the solution.

 

thank you i have checked the d+ and d- and the usb type c was not soldered well after i solder it again it works
View attachment 354663

You passed the test. This sort of thing happens even to the grey hairs.