Decision help around Raspi's and clone's

W

waasnsteffl

HI,
May be someone could help for choosing the right hardware of raspi compatibles for the following project, as my little hardware specific knowlege is from the 80's.
I like to use a small,very little power consuming, hardware of those for reading out gps, do a 3D normalisation with kalman filter, then display only points on a 6" e-paper about ever 2 seconds and store the data on the SD card.
its for sailing races to help determine the course and when it is time to tack. also for later reading and learning about the tactical errors.

my experience, freebsd since 90's, good C knowledge (especially serial and tcp communication between the world an mainframes), little hardware knowledge

i would prefer freebsd over any other system
would a raspi zero clone be fast enough
which clone would one suggest
input only from serial gps, a small hex keyboard or similar, may be 4 to 6 keys only
a 6" e-paper interface, no touch screen
a speaker would be fine
power from lipos

i do not want to use a handy. as not bright enough in sunshine

all would be placed in a wooden box with glass window, switch and keyboard
Thanks for reading and any suggestions
Anton
 
Complex question.

First, my experience with FreeBSD on RPi has not been great; things just work much more seamlessly using Raspbian = Debian. But then, I was using GPIO and things that depend on GPIO such as i2c and 1wire: On Raspbian they are effortless, on FreeBSD they were research projects. Since you probably won't have interesting hardware interfaces (only serial for display, and simple GPIO), FreeBSD might do well for you. It's also possible and likely that there has been much progress.

From a CPU power viewpoint, I think that in C/C++, the Pi Zero will be more than sufficient. I've used my Pi0W for data acquisition at 10Hz, with network interfacing via real RPCs, plus a cell modem interface, and all that in Python, and it worked fine. Also, the Zero uses less power, which will help with your batteries.

I would definitely not use a wooden box, but something really waterproof. Go to Digikey, and start searching for enclosures with IP67 ratings. I have one that is supposed to be used for a RPi0W with cell modem and one cable (going through a watertight gland) to power supply and data acquisition, outdoors. For Window, use plexiglass (acrylic) or lexan (polycarbonate), since it has harder to break, and seal it with a good silicon RTV to the plastic box. Finding keys or buttons that actually seal against the water and wind on a sailboat will be a challenge.

On the power side: A RPi0 uses low hundreds of mA at 5V. That means you will need very significant batteries, not just a little 1000mAh cell. My suggestion would be this: Instead of using a real RPi (and running a real OS on it), try the new Raspberry Pi Pico. No operating system, no standard library, but you can use C or Python, and it has plenty of hardware IO. That cuts the power consumption down to dozens of mA. I've been toying with the idea of spending a few weekends with a project using one of those.
 
Dear Ralphbsz - Thank You very much for this comprehensive and helpful answer!!

I was not shure, if a Pi-zero clone could be fast enough. At the moment i am preparing our boat (www.s-kreuzer.at), 100 things to do. and learn about the Pico, especially if i could be successfull with no OS and library....
Thanks, Anton
 
I am messing with Mini-PCIe GPS modules from Advantec which is USB Signaling half length module.
Same slot requirements as cellular modems.
buy.advantech.com

EWM-G108H01E

GPS/GNSS Half-size Mini PCIe Card
buy.advantech.com buy.advantech.com

My plan is Hummingboard2 which has MiniPCIe slot with SIM on bottom.
eInk Display sounds interesting. Will it hold up?

My Module is pulling 100ma.
ugen2.2: <u-blox AG - www.u-blox.com u-blox 6 - GNSS Receiver> at usbus2, cfg=0 md=HOST spd=FULL (12Mbps) pwr=ON (100mA)

I ditched LIPO and went small SLA.
I am experimenting with 6V-4.5Ah w/LM7805 knockdown.
I have some lipo packs but I would not recommend them for heavy jarring of maritime use.

We have a port of Open chartplotter/navigator with inputs for GPS.
astro/opencpn
 
Why all these ports?

I would write a little bit of C/C++ code, link it with some lightweight drawing library, a tiny bit of data storage (for the maps and perhaps logs), and be done. I don't think this applications needs an OS, nor a file system, nor a GUI kit like X11.
 
Thanks for all the help!
Probably i will try Ralphsz hint with the pico.
The case will be cfk mahagony laminated with plexy glass, which i can easily do ( sailed wooden regatta boats, self restaurated, 15er ad 20er so called jollenkreuzer https://www.20r.at/galerien/)
accu probably li-ion 16850, which i am experienced with.
gps, epaper still open
as the case is in direct sun, cooling will probably be necessary, my be alu backside...
every hint is wellcome.
greetins and thanks, anton
 
ePaper / eInk general: check that the temperatures you are operating in are within the temperature ranges of the display you choose.
 
For embedded stuff, sometimes a full OS isn't needed. RealTime OSes, like FreeRTOS might be better.

Also, something as simple as this - might not need a SBC, like the raspi. Look into espressif esp8266 and ESP32 line ... which might be more inline what you are looking for.
 
hi,
good hint with tempratue range of epaper.

if i would not use an OS, could i fall into interrupt problems when reading/sending to multiple serial lines, whithout specific programming?

in case i use rtos, which i used in the late 80's, would that increase significantly power consuming.
this has been the last time i worked with hardware...
 
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