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<p>Hi Dwight,</p>
<p> Scott shared a ton of links that have some interesting info,
but I wonder if we're straying from the root issue? <br>
</p>
<p> I was confused by your posting because the ESP-WROOM-32 is a
module and has no USB capability whatsoever. Waiting for a serial
device to show up on your PC would be a long wait. :-) So I'm
guessing you're either using a USB to serial dongle that supplies
some amount of 3.3 volt current, in which case the "serial port
refuses to show up" is <i>100% to do with the dongle and 0% to do
with the ESP32 module</i>, or else you're using some kind of
dev/carrier board that has a USB interface. If it's the former,
then which dongle?? If it's the latter, please let us know
precisely what thing you're using that has the module on it. For
instance an Espressive dev board from Adafruit, an ESP32 Thing
from Sparkfun, a ____ from Alibaba, etc. Point us to an
informative web page describing this thing you speak of, or the
corresponding page for the serial to USB converter being used with
the raw module. <br>
</p>
<p> But, in the meantime, let's look at actual power requirements
for the module. Here's a <a moz-do-not-send="true"
href="https://www.espressif.com/en/products/hardware/esp-wroom-32/overview">picture
on the Espressif web site</a>. If you click the black box called
"documents" on the left margin, then click "PDF documents" you get
a page of stuff. Scrolling down a bit there is a section for
ESP-WROOM-32, including an "ESP-WROOM-32 datasheet" row. If you
click "download" there you'll get the <a moz-do-not-send="true"
href="https://www.espressif.com/sites/default/files/documentation/esp-wroom-32_datasheet_en.pdf">module
datasheet</a>. Notice page nine where it says the absolute
maximum power supply voltage is 3.6 volts. The absolute minimum is
2.7 volts. The minimum current is .5 amperes, but the implication
is for *everything going flat out*. That is, both cores pegged
doing as much computation as they can manage, beating on memory,
and both WIFI and Bluetooth radios honking as fast as they'll go.
This right here would seem to be a sticking point for that
ESP32-Radio repository issue Scott pointed to: it has "the
specific question", but nothing like your specific hardware. With
that thing the guy's GitHub repo is to do with running the WROOM
module, an SPI to audio board, and a TFT display with god knows
how much backlight current, all off a USB port via some
undisclosed carrier board or dongle, maybe hacking into the 800mA
max 5 to 3.3V linear regulator on the audio board. But this
doesn't apply to your circumstance, does it? I don't think so
either. On the other hand, if you've been using a dongle set to
supply five volts to the module vs 3.3 that might have fried your
module since it far exceeds the absolute maximum supply voltage
listed in the datasheet. If you have it supplying 3.3 volts it
might be way too wimpy to supply enough current to your module.</p>
<p> And it's possible the dongle is being yanked so hard trying to
power the ESP32 module that it's USB serial chip won't function.
So a question (if you're using a dongle!) is whether the "comm
port shows up" with it disconnected from the module but "fails to
show up" when connected.<br>
</p>
<p> The standard current limit for a USB jack from a PC or laptop
is supposed to be 1/2 amp and that just happens to be what the
Espressif module datasheet lists as a minimum. Because five to 3.3
volt regulators just throw away power, 1/2 amp coming in at the
USB 5 volt supply level is only going to give 1/2 amp out at 3.3
volts as a theoretical value: real chips will be a bit less, but
not much less as long as their rated output current capacity is at
least 1/2 amp (the one in the "radio system" Scott pointed two on
the audio board is good for 8/10 amp, so all but a smidge of the
USB port's 1/2 amp should be available). Also, the real limits for
these USB ports are going to vary, and if you're using outboard
hubs some of those might offer hugely higher current for charging
cell phones, etc. But, if you stuck your two series AA cells
across pins 1 and 2 of the module, that might be relevant to a
power issue if the AA cells are totally fresh and not sagging
below the datasheet minimum supply requirement of 2.7 volts.</p>
<p> Except my hunch the basic problem isn't power (YET), instead
it's to do with communication between whatever it is your PC USB
is connected to and your host OS.</p>
<p> So, let us know what the exact hardware is (a link to the page
advertising the thing would probably be the best starting point)
and we can focus on whether you need a driver for one of the many
serial to USB chips used on the various carrier boards, or what. I
assume you know about the Windows "device manager" window and
you've confirmed how a new COM is not appearing/disappearing as
expected when you connect/disconnect your USB cable?<br>
</p>
<p> So hopefully once we get a handle on your hardware environment
somebody who has used the same one can chime in. My belief is that
until the ESP32 starts vigorously beating on the WIFI and
Bluetooth radios it's current requirement isn't going to flirt
with the 500mA minimum. So I think you should set aside the
battery experiments for the time being.</p>
<p> But as an FYI, I have the necessary equipment to confirm
marginal supply situations and make precision DMM logs and 'scope
pictures and the like to nail down exactly what's happening if
this ends up being a secondary problem once you get your comm port
or serial device to appear as expected. <br>
</p>
<p> Finally, this is the long winded novelette that comes of going
"the other way" vs asking you, up front, for more information. :-)<br>
</p>
<p> Hopefully you can bring your setup to the February 12th meeting
so proper salivation can be stimulated. The ESP32 is a truely
awesome piece of hardware and I for one am excited to see you
working with this and look forward to hearing more details.<br>
</p>
Best Regards,<br>
Pete<br>
<br>
<div class="moz-cite-prefix">On 01/27/2018 09:29 PM, Dwight Morgan
via TriEmbed wrote:<br>
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<p class="MsoNormal">I just got an ESP-WROOM-32 and I’m having
trouble just getting it set up. I’m going through all the
instructions for Arduino and Git but the serial port refuses
to show up. I read in one forum where it needs a separate
power source because the USB is not enough so I connected two
AA batteries to the 3v3 (for 3 volts) and ground along with
the USB to load a simple sketch, but no dice, no serial in the
Arduino tools menu to select. I remember some time ago seeing
one of the Triembed meetings on the ESP32 but I can’t find it
on the website. <o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">I hope somebody is using the ESP32 and can
shed light on this problem. Any help is appreciated.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Thanks,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Dwight<o:p></o:p></p>
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