CP2104 Serial Adapter

VoltLink revB CP2102N USB Serial Bridge & ESP32 Programmer | Voltlog #396

Welcome to a new Voltlog, a rather short video for today. I’m gonna be introducing this little guy. You might recognize the design, it’s my VoltLink USB to Serial Converter but in it’s latest revision B which has a few important upgrades over the previous one and these are things that I noticed while using the module almost daily so I think you will all agree with me that these were some good improvements that justified revB.

In general I tried to keep the board the same size, because I like this form factor, the arrangement of the connectors, the fact that I have my own VoltLink standard JST connector that i use for all of the boards that I design so all of that stayed the same but due to the ongoing chip shortage I had to pick a slightly different usb to serial chip, we are now using the CP2102 in QFN28 package. So generally this chip is very similar to the previous version except that it’s a bit newer but you still get up to 3M baud rates which is great. Because of the new chip this meant redesigning the passives to support this new chip and redoing the layout.

Also because of the ongoing chip shortage, prices for electronic components have gone up in the past year and I will have to run the numbers for this particular design but I have no choice but to increase the cost of the unit on my Tindie store if I am to continue making these.

I also upgraded to a USB full speed rated ESD protection diode with lower capacitance TPSP0503, this should mean no connection issues while at the same time offering the recommended protection level on the USB connection together with the PTC resettable fuse.

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.

VoltLink™ A Fancy USB Serial Adapter (ESP32 Programmer) – Voltlog #356

Welcome to a new Voltlog, today I’ll be showing you how I created my own usb to serial adapter board and we’ll go through some of the design decisions I had to make and I will explain the reasoning behind making these choices but first let me tell you the background of the story, Personally I’ve always liked having my own usb to serial adapter and here is one that I designed something like 10 years ago maybe more. The layout is not great, my PCB skills were obviously not as good as they are today but nonetheless, I created this adapter as an exercise but also for the important purpose of having a reliable and flexible tool. Reliable because I could control the chip that I’m using. It was a Silabs CP2103 and I was getting it from a well known distributor.

Flexible because I had all the IOs of the chip broen out to 0.1 inch headers which could mean that I had the option to trigger a reset on a particular board or something along those lines. And I’ve also designed other adapters based on FTDI chips and more recently based on the CH340 family of chinese chips.

So this brings me to today’s project, I designed this new adapter for two reasons: one is the good old reason of reliability, you can’t trust the adapters you’re getting from aliexpress, they’re almost always using fake chips and generally are of lower build quality. I want a reliable CP2104 series chip in here, I want it to be able to sustain high bit rates for fast uploading of firmware images to target boards.