Silabs CP2104 No Activity on RX TX LEDs Bug – Voltlog #359

In Voltlog #357 I talked about a bug affecting the programming of ESP32 modules via Serial Bootloader, basically the issue was caused by an incorrect reset sequence regarding the EN and IO0 signals and I also showed a fix which involved adding a capacitor to delay the EN line.

Well, this week I’m gonna show you another bug which I encountered recently but this time with the CP2104 USB to serial converter chip from Silabs. So recently I designed this little board called VoltLink, it’s basically a usb to serial converter board but one that also integrates the auto-reset circuitry needed for programming Espressif modules like the ESP8266 & ESP32. I also have a 1mm pitch JST-SH connector with a standard pinout that I use in all of my designs and this helps with space savings on small circuit boards.

Well after assembling one of these boards, I connected it to my computer, the new virtual serial port was created and I thought everything was running fine, except it wasn’t. I quickly discovered that the status LEDs were not reacting when there was communication on the serial lines. I don’t know about you but I want my status LEDs to be functional, it helps me get a quick visual understanding of the communication happening on the serial lines. I don’t need anything specific, I just need to know that there is activity and if there is a lot of activity or less activity.

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