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I am developing a small electronic product which, if all works fine, I think about producing and selling in small numbers.

Currently I use an ESP32 DevKit for the development. That is the ESP32 development board with "everything" included like power regulator, USB connection, etc. https://www.aliexpress.com/item/4000093185394.html

The schematic for that DevKit is published here https://www.espressif.com/en/support/download/documents

In theory, when I want to build my own product I could:

A) Use all or most of the PCB design of that DevKit board and add the few extra components which I need all in one PCB.

B) Or I could design my own PCB and solder the DevKit board on my PCB which would include only a few extra components.

B is much easier for me because the DevKit boards are ready and cheap available.

Is it good practice to do that? Or are there good reasons to put everything on one PCB including the parts which are now on the ESP32 DevKit board?

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  • \$\begingroup\$ You have to ask and answer all those questions yourself. It might be fine practice to use a Dev kit for a one off chicken hatchery project, for example. Or sell a few. So long as it meets the needs with the price for it, and you can support your customers the way they should be, then it may not matter much. Or it may matter a lot. Since your don't tell us what you are doing, there's no chance to venture even an opinion, let alone an educated one. I don't see how anyone can help you in this. Not with as much as you've written. \$\endgroup\$ – jonk Dec 18 '19 at 6:25
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    \$\begingroup\$ You would have to check whether you are legally allowed to use the dev kit in a product (see related question electronics.stackexchange.com/questions/67030/…). And you might consider whether compliance with codes and standards is feasible when you are using a dev kit (see this question electronics.stackexchange.com/questions/332208/…) \$\endgroup\$ – oliver Dec 18 '19 at 6:35
  • \$\begingroup\$ That being said, I think it doesn't make sense to just "copy" the dev kit layout to your own board if you don't at least change the layout (e.g. in order to better comply with EMC regulations) or achieve lower cost by doing so. \$\endgroup\$ – oliver Dec 18 '19 at 6:42
  • \$\begingroup\$ And honestly, I would ask myself the question whether security could be a concern (which I think is more probable for small scale products). If I were Xi Jinping, and if I wanted to rule the world in the James Bond villain fashion, then I guess the first thing I would do is to flood the world with a cheap IOT component that eventually would allow me to turn off critical infrastructure by pressing a red button on my desk. \$\endgroup\$ – oliver Dec 18 '19 at 6:51
  • \$\begingroup\$ @oliver yeah right. \$\endgroup\$ – Bruce Abbott Dec 18 '19 at 7:00
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I use dev boards because they save me time, are known to work, should have met the required EMC standards, are easier to install and maintain, and if I drop dead the person taking over my project won't have too much trouble figuring it out.

If you make your own rf PCB, or use a part of the dev board modified in any way that could affect EMC compliance then you will probably have to get it tested to be legal, which would be prohibitively expensive for a small production run. All this is avoided if you use a pre-approved board.

Conspiracy theories aside, buying from AliExpress or eBay is a bit risky because you don't know if the device is compliant, even if it looks identical to one that does. If you are worried about it then buy from a reputable company like Sparkfun or Digikey. If that still doesn't assuage your fears then sell the product without the module and let the customers source it themselves.

Also consider the application - might it put you at the wrong end of a lawsuit if something goes wrong? If it's a 'hobby' project and you aren't making a lot of money out of it then you probably have nothing to worry about. Millions of these EPS32 modules are being used throughout the World, so if they were a problem we probably would have heard about it. But you have to evaluate the risk. If there's even a small possibility that your product could cause harm then it might be best not to sell it.

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  • \$\begingroup\$ Don't wanna be obtrusive on the security point. But "we probably would have heard about it" is not a valid argument because there might be a backdoor in the hardware that is only exploited in a very specific scenario. If one uses the ESP to control the lighting of a fishtank, that might be irrelevant, but already for a smart home application I would be cautious. Call that conspiracy theory if you want, or just accept that people arrive at different risk priorities. \$\endgroup\$ – oliver Dec 18 '19 at 8:40
  • \$\begingroup\$ Man what the actual f... You point him out with "We probably would have heard about it" and then saying its not a valid argument. But then carries on with "There MIGHT be a backdoor" - "Only exploited in a very specific scenario" .. Do you hear yourself ? \$\endgroup\$ – Sorenp Dec 18 '19 at 8:59
  • \$\begingroup\$ @Sorenp: calm down, this is not your favorite social harassment platform. Have you even heard about the term risk management? It is very common in engineering and it actually deals with eventualities. By the way, I can't hear myself, but probably you can... \$\endgroup\$ – oliver Dec 18 '19 at 9:11
  • \$\begingroup\$ By 'a problem' I was talking about the possibility of causing interference in normal operation, not hypothetical 'back doors' put into the chip by James Bond style villains. But hey, that's why I went back to using my 1992 Amiga 1200 to browse the web - with a CPU too simple to hide a back door in and the OS in mask-ROM so it can't be hacked. I also wrote my own network driver, and disassembled the web browser to make sure there was nothing hidden in it. Scammers and the NSA can't touch me when I use that machine! (especially when I wear my tinfoil hat...). \$\endgroup\$ – Bruce Abbott Dec 18 '19 at 9:12
  • \$\begingroup\$ @BruceAbbott: what is so wrong about recommending the OP to make a risk assessment that deals with a (possibly remote) probability that there might be a backdoor. In fact backdoors are not that uncommon as you seem to indicate by using the term "conspiracy theories". Notice that a conspiracy theorist would claim that there IS a backdoor, whereas I only say that there COULD be a backdoor for good reason. But somehow I seem to have hit a sensitive spot by mentioning this. \$\endgroup\$ – oliver Dec 18 '19 at 9:17
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A number of development board makers specify that they are not to be sold in commercial products. They are usually sold at very low prices with little or no profit margin by companies wanting to sell the chips. This is true of ST Microelectronics, for example. Now, for small production runs and low sales you can probably get away with ignoring this, but if it comes to their attention it could cause problems.

On the other hand, copying what they have is quite legitimate as long as you make your own boards.

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