ESP32 Bootloader Tool

VoltLink Shelly Adapter Test Jig | Voltlog #426

Welcome to a new video it’s been a while since I’ve done a project video on the channel and it’s not that I’ve not done any projects, I’ve designed lots of things this year it’s just that they’re part of my consulting business, under an NDA so they can’t be shared.

You may be familiar with the VoltLink, the usb to serial adapter that I designed a while ago, it’s quite popular on my Tindie store with lots of orders coming in and for good reason if you ask me, this is an awesome, reliable usb to serial adapter. To extend its functionality I also created this Shelly relay adapter which can be used to flash shelly relays, in a safe and reliable way by also powering the relay during the flashing procedure so you don’t need to have it connected to mains.

If you would like to order a VoltLink, you can find these on my Tindie store, there will be a link in the description of the video so check it out.

So far I haven’t any issues, not one single module with problems and I’ve probably made several hundreds of these. It’s a pretty simple design in terms of PCB, the components are 0603 so there isn’t much that can go wrong but recently I’ve started thinking about testing these.

Now the topic of test jigs and testing electronics in general can get pretty deep, especially if you need to implement it in the manufacturing process and keep track of the test results in an automated fashion but for hobby level it can be much simpler.

For example, depending on the number of units you manufacture, you can also skip testing all together, because if I sell 100 boards and 1 of them ends up defective, I can live with that 1 failure rate and I can cover the cost of shipping another board to that customer and all of this with zero resources wasted testing these but at the expense of one unhappy customer who needs to wait for another unit to be shipped.

So mainly for me that was the main factor for wanting to test these, to avoid having unhappy customers that might end up getting a bad unit. And I don’t really need to test for all of the things working, I just need to figure out if I have a working connection from the USB side all the way up to the shelly relay and also verify that the path can be used to communicate over serial and toggle the reset lines.

This kind of test would eliminate for example a lot of the most common issue like soldering problems with the USB Type-C connector or with the QFN chip, or with the PCB copper layers, or with the JST-SH pigtail connecting the adapter board, or soldering issues on the small adapter board so all of these would be eliminated.

So here is what I came up with, a series of 6 total shelly adapters, chained together in series with an ESP32 at the end of the chain. I would be connecting a VoltLink at the start of the chain, UART signal would then go through 6 of these adapters, connectors, pigtails and it would end up at the ESP32 side for either flashing the ESP32 or writing a small test firmware that would just communicate over serial to verify the whole chain is connected correctly.

VoltLink revD USB Serial Bridge & ESP32 Programmer | Voltlog #414

Ever since I’ve started offering the option for the Shelly programming cable, lots of people have ordered one because it makes the job of flashing an otherwise dangerously mains connected relay very safe by not having to power it from mains, but just supply it with DC power from the VoltLink itself.

But this video is not about that, it’s about the latest revision D of the board, the changes that it contains and some future plans.

So as you may have noticed there is no power LED on the VoltLink and to be honest for my personal use case I don’t really need one but I do understand people that want a power status LED so that they get a quick glimpse of whether the board has power or not.

Personally I think that because the VoltLink is so reliable in operation, the power LED is redundant but I do remember the times when I was using other cheap usb to serial adapters, there were the occasional issues with the micro usb connectors failing, with the on board chip failing, so it was nice to be able to see that you still got power to the board at least. Nonetheless, I added one to the new revision, placed it right next to the USB connector.

Now because I added these two extra components to my schematic, the LED and the resistor, I decided to switch to a resistor network to replace 4 x 1kilohm resistors with a single package to further optimize my BOM cost and DFM.

Another small change I did was to bump the 4.7uF decoupling capacitor on the USB to serial chip to 10uF because I was already using that value at the output of the voltage regulator. This once again, optimizes my BOM for using less parts as this will become important later.

And while I was revising the PCB, I also switched to these nice labels created with the Kibuzzard plugin for Kicad. No extra functionality because of these, but they do look nice.

VoltLink revC CP2102N USB Serial Bridge & ESP32 Programmer | Voltlog #405

Welcome to a new Voltlog, a rather short video for today. I’m gonna be showing you the latest revision of the VoltLink USB To Serial Adapter. This is revision C and while this revision doesn’t necessarily bring any new functionality to the VoltLink it does optimize the design for manufacturing a little more which makes it easier for me to build these units.

Before I go into more details let me just quickly mention that if you would like to order one of these, they are available on Tindie and there will be links in the video description to the product page.

So like I mentioned, no new functionality added in revC, but that’s okay because I’m pretty happy with the functionality we have so far, I mean there is USB Type-C which means you no longer need to resort to the older micro usb cables, you got over current protection at 500mA, ESD protection.

We still have a high quality, high speed, usb to serial converter in the form of the CP2102N which enables baud rates up to 3M baud and this significantly improves the time you need to flash your board and you will quickly get used to this higher speed so much that when you switch to some other converter or board that only supports lower baud rate you will feel how slow that is.

We still have the 500mA rated low dropout regulator which provides 3.3V to the target board and 500mA is enough to cover the majority of boards that you will be programming. For example all of the ESP32 based boards that I design can be powered by the VoltLink while flashing firmware with no issues. Additionally I showed in a recent video that with a custom optional cable that you can order with the VoltLink you can safely flash Shelly relays without having them connected to mains voltage.

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.

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.