Hey all, we've had to cancel today's Zoom meeting. We had some issues with the BME680 (floating point) and couldn't get fully-functional code together in time for the presentation.
If somebody would like to run a P2 Live Forum today without a topic, that's fully welcome and appreciated! Chip is unable to participate and I'm out of town as well.
@Nix said:
Hi guys. I'm not sure as to how this all works.
Is my assumption correct that the next one is in September?
This thread is very fluent. It changes day to day. someone may come up with a segment this week that may go online this Wed-Thur this week. Keep checking this thread or sign up at Parallax for updates.
I'm just listening to the previous session where Chip's use of single letter variables is brought up during a discussion about adding floating point to Spin2.
Just thought I'd highlight a reason why Chip always uses x, y, z in lots of examples. It all originates from a lifetime (on-going) of assembly coding. In assembly, scratch variables/registers are a big fact of life. Higher level languages take away much of the need for scratch space.
PS: By scratch, I mean a set of variables that are reused for multiple uses as the code executes. Even to the point of containing differing data types at different times. Stack can perform this as well and is often how the higher level languages achieve their scratch ops behind the scenes.
Later in the session is questions on motor drive design. I'll make some comments:
- Hall sensors are open-collector and can run happily at 10 volts. Don't need to have 5 volts just for that.
- The powerFETs are self protected in that arrangement. Chip is correct about them.
- The question around the bus voltage is one of regeneration, not spike protection. ie: Need to dump motor breaking energy. Varistors aren't good at dissipating excess energy at all. Not unless you can get one with a heatsink mount. Maybe such exists, dunno. In industrial drives, for basic regen protection, they have heatsink mounted dump resistors with an extra dump transistor for switching it in. In heavier inertia loads they use vented nichrome heater elements for dumping excess energy.
- There's no point in having electrolytic canister capacitors higher voltage than absolute max voltage rating of the powerFETs. Using voltages any higher will destroy the transistors. Certainly spec'ing both at 2x or 3x the operating voltage is nice though. It gives leeway for regen without having to dump.
Here's my list of system mailboxes as per Peter's early (years back) comments:
hw_rev long 0 'hubRAM byte addr $010 - unused reserved parameter - using to hold revA/B
clk_freq long 25_000_000 'hubRAM byte addr $014 - sysclock frequency, integer frequency in hertz
clk_mode long 0 'hubRAM byte addr $018 - clock mode config word, used directly in HUBSET
asyn_baud long 230_400 'hubRAM byte addr $01c - comport baud rate, integer baud in hertz
Comments
@ hinv Great References:
http://web.wpi.edu/Pubs/E-project/Available/E-project-042711-190851/unrestricted/PWM_Techniques_final.pdf and https://www.ti.com/lit/an/slaa602a/slaa602a.pdf
Hey all, no P2 Live Forum this week, unless one of our community members is willing to host (in this case, I'd sign on and pass Host to you).
Chip is out of commission for a couple of days and I've got to get ready for a conference/inventory count.
Next week we return with the @JonnyMac!
Ken Gracey
JonnyMac has jury duty this week! Sorry, gang -- I am looking forward to seeing everyone online again -- but it won't be this week.
I suppose a live cross to Jury duty is out of the question? They probably have rules about that
Sign up right here!
https://us02web.zoom.us/meeting/register/tZIvd-GgrDojHdN9P6SfXINMuZklqlL7atxR
Ken Gracey
The first post has been updated with links to several recent videos.
Ken Gracey
Regarding this info. from the 1st page of this thread:
Propeller 2 Live Forum: BME680 Environmental Sensor Object with JonnyMac
Wednesday, July 7th at 1:00 pm Pacific
https://us02web.zoom.us/meeting/register/tZAkd-mrqT0rHt09TvVBx8YqW2fpmJmIY1yC
I get an "Uh oh!" from Zoom when I click the link.
Hey all, we've had to cancel today's Zoom meeting. We had some issues with the BME680 (floating point) and couldn't get fully-functional code together in time for the presentation.
If somebody would like to run a P2 Live Forum today without a topic, that's fully welcome and appreciated! Chip is unable to participate and I'm out of town as well.
Ken Gracey
Ah, that explains it. Thanks, Ken.
Big push to finish the docs ... and throw some projects in the mix ... Sounds like it's getting a bit hectic at Parallax.
Registration link on the first post!
Ken Gracey
Ken, unfortunately I missed it as when I checked last night before retiring nothing was posted
It's been moved to tonight (Thursday) this week.
Oh thanks for pointing this out as it’s already Thursday evening here. Forgot about being a day ahead.
Hi guys. I'm not sure as to how this all works.
Is my assumption correct that the next one is in September?
This thread is very fluent. It changes day to day. someone may come up with a segment this week that may go online this Wed-Thur this week. Keep checking this thread or sign up at Parallax for updates.
Registration link on first post! See ya Thursday.
Ken Gracey
shoot I missed it.
Mike
It's up on YouTube already! Fast turnaround.
I'm just listening to the previous session where Chip's use of single letter variables is brought up during a discussion about adding floating point to Spin2.
Just thought I'd highlight a reason why Chip always uses x, y, z in lots of examples. It all originates from a lifetime (on-going) of assembly coding. In assembly, scratch variables/registers are a big fact of life. Higher level languages take away much of the need for scratch space.
PS: By scratch, I mean a set of variables that are reused for multiple uses as the code executes. Even to the point of containing differing data types at different times. Stack can perform this as well and is often how the higher level languages achieve their scratch ops behind the scenes.
Later in the session is questions on motor drive design. I'll make some comments:
- Hall sensors are open-collector and can run happily at 10 volts. Don't need to have 5 volts just for that.
- The powerFETs are self protected in that arrangement. Chip is correct about them.
- The question around the bus voltage is one of regeneration, not spike protection. ie: Need to dump motor breaking energy. Varistors aren't good at dissipating excess energy at all. Not unless you can get one with a heatsink mount. Maybe such exists, dunno. In industrial drives, for basic regen protection, they have heatsink mounted dump resistors with an extra dump transistor for switching it in. In heavier inertia loads they use vented nichrome heater elements for dumping excess energy.
- There's no point in having electrolytic canister capacitors higher voltage than absolute max voltage rating of the powerFETs. Using voltages any higher will destroy the transistors. Certainly spec'ing both at 2x or 3x the operating voltage is nice though. It gives leeway for regen without having to dump.
cool,
and i am gone...
.. and back, there is no August 5 zoom, sad
Mike
BTW: Tranzorbs/Transils are not varistors, they are fat zenor diodes. None of those are suitable for dumping regenerative energy.
Here's my list of system mailboxes as per Peter's early (years back) comments:
Address $10 (hw_rev) I've made up myself.
It's here:
thx
Mike
28 minutes in is a photo of where the CNC mills and lathe are now located. The building space looks to be an old bakery.
EDIT: Oh, an old Tortilla factory.
Yeah,
Parallax is OUTSOURCING. But not to China, to Red Bluff....
Enjoy!
Mike
I guess I have been censored. Was that you Ken?
Registration link on the first post!
See ya there, tomorrow.
Ken Gracey