I recently made a USB to UART circuit using a silicon labs chip CP2102N-A02-GQFN24 for my homemade espresso machine's motherboard. I have used a similar silicon labs chip before successfully to upload firmware to MCU but because of this chip shortage I could not get my hands on the one I typically use. The circuit is meant to upload firmware from my laptop to an MCU (ESP32). But as soon as I plug in the micro-USB I get the device not recognized error, which I know is bad news.
I have verified the chip is receiving the 3.3V supply voltage, verified component placements, and checked for shorts on the bridge chip. But I am at a loss of what could be causing the problem, does anyone know what the heck I am doing wrong?
Edit:
I rearranged the wires in the USB cable that I connect to this board to match the incorrect usb pin order on the PCB as pointed out by brhans. Not sure how this error was made! After doing so the device was recognized. But just one problem, all firmware uploads fail to connect to the MCU. I have included 2 additional diagrams from the help text which I thought would aid in locating the problem. The first one is the diagram I use for the power scheme of this chip and the second is the data connection scheme. Combining these two diagrams gives the entire circuit, and I think that based on this information my circuit should be working, but clearly this is not the case.
One red flag that I see is that the manual lists 3 power supply options, of which I chose option 3 (device internal regulator not used). The manual then goes on to list how to connect the data pins which is the other image I shared. However, they only list two layouts, which are bus powered and self powered. I don't think this covers my power scenario, but I am not sure what I would do here…
Best Answer
You need to power VIO, most likely 3V3 on your case.
Page 29 of the datasheet:
5 VIO I/O Supply Power Input