I spent some time on the handlebar mount. Here’s what I came up with so far. The idea is to have a general purpose baseplate that could get attached to pretty much anything. For a quick setup one could use this simple inexpensive camera mount:
It’s not a major issue. It still wouldn’t collide with anything inside the Megan housing. It just looks ugly. This is just a grub screw though and it’s easy to replace for a shorter one – if one can find it. This is a 1/4"-20 UNC thread. Not so easy to find in the EU (though it does exist).
Any comments or suggestions would be much appreciated.
You could make the plate thicker for more thread engagement, but seems pretty good otherwise. Maybe some more holes, like M4 or M5 in a square pattern for custom solutions would be nice?
If I were to source a Beitian BK-182 for racing, would it just use the same existing plug/socket? Are any additional setups needed to get 25Hz gps on the Minnie? Would I get much less ride time storage? Also can the Minnie be bought without the GPS module?
Yes. They keep changing the cables though so make sure the cable you got with the GPS module connects the pins correctly. You may need to repin the cable. Minnie GPS pins are clearly labeled:
No. But you won’t get 25 Hz logs either. Let me explain how logging works.
A single data point consists of the data from all VESCs and from the GPS. The data is collected asynchronously. On a time line it may look something like this:
GPS packet 1 received
GPS packet 2 received
VESC packet 1 received
GPS packet 3 received
VESC packet 2 received
GPS packet 4 received
GPS packet 5 received
VESC packet 3 received
Now, we log anytime we receive a VESC packet and we associate it with the latest GPS packet. So in the example above, the log would contain:
VESC p1, GPS p2
VESC p2, GPS p3
VESC p3, GPS p5
The GPS p1 and p4 would be dropped.
The VESC data logging frequency is the constraining factor. This frequency depends on how many VESCs there are in the system (“VESC p1” would actually be the data from all VESCs). If I remember correctly, the best we were able to do in our tests was around 10 Hz.
So even if you have a 25 Hz GPS, Minnie currently won’t be able to log all the 25 GPS data points per second.
Also, there are 3 fidelity modes – high, normal, low. With high, we log everything as quickly as possible. With normal and low we drop some data points to save space. This can be easily changed in the Metr app. You will obviously want high if you’re after the highest possible resolution.
Not at the moment but we can allow it if there’s interest.
Are there 3D files available anywhere for the MEGAN/baseplate?
I’m finishing up a pretty non-standard board build right now, and want to add a MEGAN to it when y’all open sales. I need to drill new mounting holes, and would ideally like to do this before I button everything up…and a 3D printed baseplate model would be the perfect way to do this.
Would it be possible to log VESC and GPS packets separately? So instead of writing like
vesc P1, GPS p2
vesc p2, GPS p3
Vesc p3, gps p5
It would be
Time t1, gps p1, _
Time t2, gps p2, _
Time t3, gps p3, vesc p1
Time t4, gps p4, _
Time t5, gps p5, vesc p2
The aim is to have a high resolution GPS log for better speed tracking. Not sure if that would be too high a data rate or much of a real improvement over 4hz, I haven’t used any formal databases beyond just “read and dump the contents of a serial port”
Of course it’s possible but it creates a special case that then needs to be handled downstream. You need a new config option for enabling this special logging mode. And then how do you even name it and how do you make it comprehensible for users. It’s all doable but nowhere near a 5 minute job.
Does anyone happen to have a picture of Stormcore CAN wiring where 5V is taken from another port? We’re preparing a Megan user guide and it would be really helpful if we could include a picture like that. We don’t have any Stormcore of our own.
