Live on CrowdSupply! muArt - A UART converter finally done right

[pylo]

Yes, you'll need the CP210x VCP drivers. You'll also be able to get them much more easily from the muArt's homepage, but that's under construction. You'll also find a much better Linux driver there, though I have to say the one in standard mainline also works. Keep a lookout for project updates over at CrowdSupply for more info

[grizewald]

Great to see this live at last.

I've just added my backing as well and I'm really looking forward to being able to get rid of my pile of USB-Serial converters!

 

[EEVblog]

Do you have to add the VCC line to the target? (presumably to power the level converter)
Forgive me if it's mentioned somewhere, I haven't looked at everything.

[pylo]

Do you have to add the VCC line to the target? (presumably to power the level converter)
Forgive me if it's mentioned somewhere, I haven't looked at everything.

No prob Yes you need that, in the latest version of the board this pin's also been renamed to VIN to emphasize that this is an input pin. In my experience every prototyping board / SBC out there already has a header for GPIO or core voltage, so I prefer very much having to connect one wire more and then everything being automatically correct, instead of having to set voltages manually. And for your own custom boards you can either place this pin too, or in case you cannot, just supply it externally, but IMHO the latter is kind of rare.

Here's an interesting thing: I deliberately made the PWR LED only light up when both USB and VIN are connected. This way you can actually tell when the whole board's powered correctly, unlike with other converters where this LED simply signalizes USB connection but is actually useless because it doesn't mean power has been correctly applied everywhere.

Aaanyway, last week I posted a sample for your mailbag, with schematics and a preliminary datasheet. If there's a mail from Hungary, that's probably it

And thanks Dave for the great vblog!

[Jon.C]

backed !

almost there

[EEVblog]

Here's an interesting thing: I deliberately made the PWR LED only light up when both USB and VIN are connected. This way you can actually tell when the whole board's powered correctly, unlike with other converters where this LED simply signalizes USB connection but is actually useless because it doesn't mean power has been correctly applied everywhere.

Nice touch.

Aaanyway, last week I posted a sample for your mailbag, with schematics and a preliminary datasheet. If there's a mail from Hungary, that's probably it

Cool, thanks.

[BNElecEng]

Just backed the project. Good luck!

[NorthGuy]

Congratulations, it's funded 

I've read your update on safety. I think it's a good idea to add to the discussion one more case - negative voltages. If they poke a ground wire into VIn then there will be negative voltages on other pins.

[chriswebb]

Backed it!

[pylo]

Congratulations, it's funded 

Thank you guys for your support! I was contemplating between 7-8 week campaign period, and went for 7 weeks only because I wanted to make sure I can ship before December (to avoid Christmas season where shipping delays go out of control), but I'd have never imagined the project gets funded in just two and a half days. I'm so glad and thank you.

I've read your update on safety. I think it's a good idea to add to the discussion one more case - negative voltages. If they poke a ground wire into VIn then there will be negative voltages on other pins.

Good point to bring this up too. The ESD diodes were chosen to be bidirectional for exactly this reason. If you connect your data lines before the power, and you reverse the polarity on power, then your data signals may be negative. Unidirectional diodes would start conducting and your own board's digital outputs would see it as a short, so there's a good chance your application would burn down. Bidirectional diodes avoid this short, but now the muArt will probably get damaged instead. This is however the more preferable way, because I'd rather protect the application circuit. You may not have a replacement for your custom circuit at hand, but a UART adapter is easily replaced. The adapter is also probably way cheaper than whatever circuit is hanging on its IOs. So, for both of these reasons, if I have to choose which to preserve like in this case, I'll save the application.

Of course, if you connect power first and only then the data lines, the picture looks different. As I've mentioned in my earlier post, I've made the power LED light up only when power on *both* sides of the muArt have been correctly applied. This means you can immediately recognize if the VIN polarity is wrong (LED won't light up), so you can correct it before attaching any IOs, and all is good.

EDIT: I've incorporated these points into the original article, but I need CrowdSupply to publish the changes. They'll probably do it after the weekend.

[Jon.C]

Hi  @pylo

So is it possible to have them before November?

or continues the campaign to the end?

Thank you

[pylo]

Hi Jon,
The campaign will run to its end. But being funded early does mean I can make some preparations earlier, which should at least lessen the probability of delays.

[edgarasf123]

Seeing this is being marketed to replace all USB to TTL devices, I have one issue. How would I connect this to a serial port that only offers 3 pins: GND, TXD, and RXD? There is no 3.3v pin.



I own 2 devices that use audio jack:

and

.

[pylo]

Hi!

Normally you'd connect the VIN pin to the 3V3 header of the device with an extra jumper cable. If your devices are housed in and you cannot open them like in your case, you need to supply the VIN pin of the converter with an external 3V3 regulator (for example a lab supply), making sure ground of the 3.3V is also connected to GND of your serial cable.

I accept the critique that in such cases you'll have an easier job with a fixed voltage 3.3V converter, though I could argument it is not the UART adapter limiting you - which *can* speak to your router and TI-83 - but the fact that a wire in the cable is not present, so it is merely a connector problem. But as I said, you can connect the adapter to any other voltage source as long as it matches the level of your IO and both are referenced to the same ground.

[analogo]

Would it be possible add to the CrowdSupply campaign/shop also the possibility to order the nice cable I see in the pictures, the one one with an IDC at on end and many dupont female connectors, each marked with a tag, on the other end?

[pylo]

Would it be possible add to the CrowdSupply campaign/shop also the possibility to order the nice cable I see in the pictures, the one one with an IDC at on end and many dupont female connectors, each marked with a tag, on the other end?

Hi analogo! That cable is included in the Cable Bundle. So if you pledge for a muArt Kit instead of a single device, you'll get that cable

[pylo]

Hi Everybody!

The last time I posted about campaign progress was when it launched, and that was six weeks ago. In-between I obviously didn't want to spam about it by posting at every possible milestone, even though the campaign has been a great success with 266% of the $7k goal reached. The end of the campaign is nearing though with only less than a week left, so I'm taking this opportunity to remind you that the next few days are your last chance to back the project, and to get your own muArt at the current price.

https://www.crowdsupply.com/pylo/muart

Even if you've already checked out the project, I recommend you take a look at the project updates posted on Crowd Supply, as they contain quite a few bits of interesting information. Though I'm sure many - especially visitors of this forum - will be familiar with the technical portions, I'm kind of proud that I managed to produce regular updates that are actually informative and aren't just progress updates.

Anyway, thanks for your support and feedback, and remember, only one week left

[Mr.B]

Backed.
Well run campaign.
Looking forward to receiving them.

[xaxaxa]

I see that you have replaced the cp2102 with a ftdi part; probably too late to say this but HT42B534 is available from LCSC for $0.3. I would personally never use FTDI parts in a product, and as a user I tend to avoid products that use FTDI parts.

[pylo]

Hi xaxaxa! The Holtek bridge has already been brought to my attention in this thread, but I couldn't use it for the respin, because it is not functionally equivalent to the CP2102N. The campaign was already running long when it turned out I need a replacement for the SiLabs part, and since I promised GPIOs for the backers and many have already backed the project, I needed to find an alternative component that also has GPIOs. Had I used the HT42B534, I would have needed to remove GPIO from the features which many backers have already pledged for. The only suitable part I found was from FTDI. I know that some of you hold a grudge against FTDI, but I see no other alternative to the CP2102N as long as I want to deliver the features originally promised in the campaign.

[mrpackethead]

I never want to see another FTDI part ever again. 

[ogden]

I know that some of you hold a grudge against FTDI, but I see no other alternative to the CP2102N as long as I want to deliver the features originally promised in the campaign.

There is alternative, but most likely you will not love it: microcontroller with USB interface.

[mrpackethead]

I never want to see another FTDI part ever again.  but still backed it.

[pylo]

There is alternative, but most likely you will not love it: microcontroller with USB interface.

It is technically an alternative, but probably no one would like it unless the FW to that uC is the product itself. The development effort and even real financial costs - think about testing, signed drivers for windows (even with cdc-acm) -  would be unacceptably high at this stage of the campaign. Developing firmware for such an IC from scratch to make it equivalent to existing pro solutions like an FTDI part with all the possible options (it is more than just getting some characters over with USB) and doing complete validation is more than worth a project on its own, and the muArt is not about that. Case in point, SiLabs for one could not get it right - I have reasons to believe that the CP2102N that I had to replace is secretly an LPC microcontroller in bubblewrap.

[ogden]

There is alternative, but most likely you will not love it: microcontroller with USB interface.

It is technically an alternative, but probably no one would like it unless the FW to that uC is the product itself.

Indeed. That's why I said you will not love it. Sorry that from beginning I was not 100% believer in this project. Now I see that you handled it very well and what's important - listened to EEVblog forum members. Case is very neat indeed. Hopefully from now everything will go smooth and backers will be happy.