[Ovmsdev] Multiple OVMS devices

Mark Webb-Johnson mark at webb-johnson.net
Tue Feb 20 10:01:59 HKT 2018

A neat and elegant solution, and a cool little tool.

Note that there is supposedly also:
make flash ESPPORT=... ESPBAUD=...
to override the menuconfig setting.

Regards, Mark.

P.S. I avoid this by ensuring I only plug in one at a time ;-)

> On 19 Feb 2018, at 9:18 AM, Stephen Casner <casner at acm.org> wrote:
> Perhaps none of you (other than Mark) have multiple OVMS v3 devices to
> connect to your computer.  I have an OVMS v3.0 plus a smaller DEVKIT-C
> module that Mark sent to me to begin the infrastructure work before
> the developer boards were available.  I want to run some other code on
> the DEVKIT-C module, so I plugged it into my Mac laptop via the same
> powered hub that I bought to support the OVMS v3.0 board.
> I discovered that the driver for the Silicon Labs CP2102 USB-to-UART
> bridge controller assigns a device name like /dev/tty.SLAB_USBtoUART19
> to the second device that is connected.  The number 19 represents how
> many times one of these devices has been connected, so if I unplug the
> second device and plug it back in again its device name will change to
> /dev/tty.SLAB_USBtoUART20.  Since that device name is configured into
> sdkconfig that means a reconfig and full rebuild each time I need to
> unplug!  Bah.
> So I went searching on the Silicon Labs forum and found that a support
> request to do something more sane was filed three years ago and has
> yet to be addressed.  But one post included a workaround which is to
> use a python script to scan the system information about the USB
> hierarchy to find the location ID corresponding to each of these
> device names.  The location ID of the port where the device is plugged
> in remains constant.  Depending upon how the devices are being used,
> that can allow using a script to learn the device name currently
> assigned to each of the physical devices (assuming that a given
> physical device is always plugged into the same port).
> I took this idea and modified components/esptool_py/Makefile.projbuild
> to invoke an added program tools/findcp2102.py to look up the serial
> port as a location ID and translate it to the current device name.
> For example, in the sdkconfig file in my work tree for the DEVKIT-C I
> have changed CONFIG_ESPTOOLPY_PORT="20-2.1" which (currently) gets
> translated to /dev/tty.SLAB_USBtoUART20 when I run make (or make
> flash or make monitor).
> If the tools/findcp2102.py program is run with no argument it will
> list the location ID and device name for all the connected CP2102
> devices.  I can know which device name belongs to each physical device
> according to the order in which I plugged them in, so that gives me
> the associated location ID.  It is also possible to see these location
> IDs in the Mac's System Report, but the numbering scheme is different.
> I've committed this change to the openvehicles/esp-idf repository.
> The change is implemented such that is has no effect if the serial
> port spec is not found as a USB location ID, so it should cause no
> harm.
>                                                        -- Steve
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