
Ask HN: How to Buy Microcontrollers? - codebeaker
I&#x27;m a electronics hobbyist who&#x27;s just about wrapping up a Pi compute module carrier board for a project. My first non-trivial PCB in fact, and it seems like it&#x27;s going to work.<p>The Pi computer module has been the most accessible way I can find to get my hands on a Broadcom processor, but still, this unit adds $35 to my BOM, from which I estimate 15-20$ to be unnecessary parts (for my application).<p>I cannot find the BCM2711B0, or the BCM2837B0 anywhere for sale on DigiKey, Mouser or Octopart.<p>Similarly the Allwinner v3, the Novatek 966660, anything by Realtek, etc.<p>Possibly I&#x27;m going about this the wrong way, I&#x27;ve never designed a product for manufacture before, probably I find a partner in Shenzhen to source them for me, but what about small run build-at-home-prototypes, should I salvage the Broadcoms from older generation raspberry pis?<p>How do actually trained, well-connected electrical engineers who aren&#x27;t solely derping around in their basement approach these kinds of issues?
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PragmaticPulp
Most large SoC vendors only sell their chips to qualified partners who enter
into contract agreements. They only want partners with significant technical
resources and commitments to significant minimum order quantities (6 figures).

> My first non-trivial PCB in fact, and it seems like it's going to work.

Building a PCB to support a modern SoC is a serious undertaking. Layout and
routing for high speed traces (DDR RAM) and power supply distribution is a
very challenging topic. Many of these SoCs are in dense BGA packages,
requiring 4, 6, or 8 layer boards with advanced features like via-in-pad as
the BGA pitch gets smaller and smaller. This is within the reach of dedicated
hobbyists, but it's something you'd want to work your way up to over several
years.

> The Pi computer module has been the most accessible way I can find to get my
> hands on a Broadcom processor, but still, this unit adds $35 to my BOM, from
> which I estimate 15-20$ to be unnecessary parts (for my application).

The Raspberry Pi compute module is a great solution to your problem. You'd be
surprise at how expensive it can be to design, develop, source, and
manufacture an equivalent solution on your own.

Sourcing a pre-built module from an SoC partner is the standard way to do
this, even for companies operating at small (<1000pc) volume. The R-Pi compute
module is particularly large, but other SoCs can be found in significantly
smaller modules. Search for "Linux system on module" to find other providers.
[http://linuxgizmos.com/](http://linuxgizmos.com/) has a news feed of module
announcements.

If you absolutely must design your own system, there are some SoC vendors who
sell to retail customers and provide open access to their documents. They are
the exception rather than the rule, so you must explicitly target these chips
from the start.

Perhaps the most well-known vendor in this category is NXP with their i.MX
series of chips. You can buy them on DigiKey and download all of the
documentation from NXP's website. If you want to get started, take a look at
their i.MX6 series: [https://www.nxp.com/products/processors-and-
microcontrollers...](https://www.nxp.com/products/processors-and-
microcontrollers/arm-processors/i-mx-applications-
processors/i-mx-6-processors:IMX6X_SERIES) .

However, even with the i.MX parts it's still a better choice to use a pre-
built iMX module for your prototype phase and even early shipping units. Prove
the product and design first, cost reduce with a custom PCB later.

~~~
codebeaker
Thank you _sincerely_ for one of the most valuable interactions I've had on
the internet in recent memory.

Perhaps I've been deceived by how "simple" the schematics for the Pi compute
module look, and overconfident after my first experience designing PCBs. There
doesn't _seem_ to be that much (that I would need) actually routed on the pi
compute module (hdmi, audio, etc, etc, etc)

I always seem to forget about NXP family of chips, but indeed NXP seems to do
an amazing job of supporting their products and pricing competitively.

Again, my sincere thanks <3

~~~
codebeaker
Reply to myself having done a bit more research

\- [https://docs.onion.io/omega2-project-book-
vol1/omega2-intro....](https://docs.onion.io/omega2-project-book-
vol1/omega2-intro.html) looks _amazing_

which I found researching and filtering in Mouser's embedded computing ->
system on module page

\- [https://eu.mouser.com/Embedded-Solutions/Computing/System-
On...](https://eu.mouser.com/Embedded-Solutions/Computing/System-On-Modules-
SOM/_/N-aez5p?Ns=Pricing|0)

~~~
DeathArrow
You might like this: [https://www.kickstarter.com/projects/onion/omega2-5-iot-
comp...](https://www.kickstarter.com/projects/onion/omega2-5-iot-computer-
with-wi-fi-powered-by-linux)

Small, runs Linux and it costs $5.

