[TriEmbed] ESP32 Help

Sun Jan 28 02:21:12 CST 2018

Hi Dwight,

   Scott shared a ton of links that have some interesting info, but I 
wonder if we're straying from the root issue?

   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 
/100% to do with the dongle and 0% to do with the ESP32 module/, 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.

   But, in the meantime, let's look at actual power requirements for the 
module.  Here's a picture on the Espressif web site 
<https://www.espressif.com/en/products/hardware/esp-wroom-32/overview>. 
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 module 
datasheet 
<https://www.espressif.com/sites/default/files/documentation/esp-wroom-32_datasheet_en.pdf>. 
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.

   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.

   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.

   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.

   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?

   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.

   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.

   Finally, this is the long winded novelette that comes of going "the 
other way" vs asking you, up front, for more information. :-)

   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.

Best Regards,
Pete

On 01/27/2018 09:29 PM, Dwight Morgan via TriEmbed wrote:
>
> 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.
>
> I hope somebody is using the ESP32 and can shed light on this problem. 
> Any help is appreciated.
>
> Thanks,
>
> Dwight
>
>
>
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