00:00 <set_> relaxing done!

00:03 <zmatt> mattb0ne: it's conceivable there's something wrong with that R30 declaration, like I said normally it comes from an #include but I was just too lazy to check which one

00:04 <zmatt> I don't *think* the declaration is wrong, but I'm also not sure I tested it

00:37 <set_> He seems he fixed it w/ a rational exchange of a register... I hope he does well!

00:39 <set_> As long as Jet Fuel is not mixed. It should be okay?

00:40 <set_> Speakin' of Jet Fuel, did anyone see the Alabama fake launch? They lit that puppy up. Za-Zoom!

00:41 <set_> Live or even on released video?

00:42 <set_> Man, just being in the field nearby must have been a sight to behold.

00:42 <set_> Anyway, so. Back to the BBB!

00:43 <set_> Thank you and, well whomever you are or a group of people there, I appreciate you making the technical docs. along w/ the coding that went into the docs pages.

13:15 <mattb0ne> for logic shifters is it necessary to power both sides of the board?

13:16 <mattb0ne> https://www.amazon.com/KeeYees-Channels-Converter-Bi-Directional-Shifter/dp/B07LG646VS

13:16 <mattb0ne> this is what I have

13:16 <mattb0ne> You figure you would only need to power one side the output but I am not sure

13:28 <zmatt> why are you using a bidirectional level shifter?

13:31 <zmatt> what you probably want in this application is just an open-drain/open-collector driver (for example made using a transistor + resistor)

13:33 <mattb0ne> I need to get to 5V for the stepper driver

13:35 <mattb0ne> @zmatt: do you have an off the shelf example of what you are talking about

13:38 <zmatt> mattb0ne: https://photos.app.goo.gl/Guf636qHLxzmdBvK9

13:38 <zmatt> there are also ICs that do this for you

13:45 <zmatt> e.g. SN74LVC2G07 (dual buffer with open-drain outputs) or SN74LVC07A (hex buffer with open-drain outputs)

13:47 <zmatt> although a level-shfiter with push-pull outputs would work just fine too

13:47 <zmatt> just don't use bidirectional level shifters unless you really really have to (e.g. for I2C)

13:47 <mattb0ne> oh ok

13:48 <zmatt> it might still work I guess, dunno, you'd need to check the datasheet of whatever you're using

13:49 <mattb0ne> ok

13:51 <zmatt> it looks like the thing you linked has no real information or datasheet, which means it has no real use and should not be used for anything :P

13:52 <zmatt> (I'm being silly here, but you really ought to know better by now than to buy stuff that has no information)

13:52 <mattb0ne> lol

13:52 <mattb0ne> I know but I can get overnight

13:52 <mattb0ne> and it is cheap

13:53 <mattb0ne> I am addicted to the speed

13:53 <mattb0ne> though I get burned every time

13:53 <mattb0ne> I am hooked on the Bezos free shipping as well

13:57 <zmatt> most likely the LV supply of this thing is the only supply that really matters, and the HV supply is only used for pull-ups

13:57 <zmatt> since it looks like it's just a FET with pull-ups on both sides

14:01 <zmatt> https://www.google.com/images?q=bidirectional+mosfet+level+shifter

14:02 <zmatt> something like that

14:02 <zmatt> is probably what that board you bought is

14:03 <zmatt> actually, hold on, how much current does that stepper driver expect?

14:03 <zmatt> typ 10 mA max 20 mA ... yeah no, that's a no-go with this kind of level shifter

14:03 <zmatt> you can't use this

14:03 <zmatt> not with a beaglebone

14:04 <zmatt> that's the problem with bidirectional level shifters, they're not actually buffers/drivers

14:04 <zmatt> and in this case you need to drive more current than you can safely do with a beaglebone gpio

14:05 <mattb0ne> oh ok

14:05 <mattb0ne> let me get that chip then

14:05 <zmatt> so use an actual buffer/driver (open-drain or push-pull, either will work), either an ic or made using a transistor like I showed

14:05 <mattb0ne> got it

14:05 <mattb0ne> is there a naming convention with the ICs

14:05 <zmatt> (or using a mosfet)

14:06 <mattb0ne> SN74LXXXXX

14:06 <mattb0ne> wondering how much flexiblity I would have

14:07 <mattb0ne> there are a lot of similar chips but not exact same name which is probably important

14:07 <mattb0ne> https://www.amazon.com/BOJACK-Values-SN74LS-Low-Power-Assortment/dp/B09YRCMSQ9/ref=sr_1_1_sspa

14:07 <zmatt> there's tons and tons of chips that would suit your needs probably

14:07 <mattb0ne> there is a whole family of chips

14:07 <mattb0ne> ok

14:07 <mattb0ne> I will do some research

14:08 <mattb0ne> I just need open drain outputs is the key

14:08 <zmatt> but SN74 also contains all sorts of logic, which isn't what you're looking for

14:08 <zmatt> open drain or push-pull, either will work in this case

14:08 <mattb0ne> ok

14:08 <mattb0ne> I will do some research and circle back just to confirm what I found will work

14:08 <zmatt> no actually, do get specifically open-drain (or open-collector)

14:09 <mattb0ne> ok

14:09 <zmatt> since if you were to get push-pull it would be 3.3V probably and that's not really what you want

14:09 <mattb0ne> ok

14:09 <zmatt> plus those might be intolerant of 5V on their output, while open-drain drivers tend to be tolerate higher voltage on their output than the supply voltage

14:11 <zmatt> https://www.ti.com/logic-voltage-translation/buffers-drivers-transceivers/noninverting/products.html?keyMatch=SN74LVC2G07&tisearch=search-everything&usecase=GPN#116=Open-collector%3BOpen-drain&480=2%3B3%3B4%3B6%3B8&0min=-0.5%3B3.3&0max=3.3%3B18&1994max=20%3B188&sort=1130;asc&

14:12 <zmatt> that's filtered to support 3.3V supply and 20 mA output current

14:13 <zmatt> inverting buffers would be fine... actually inverting might be better here

14:17 <zmatt> https://www.ti.com/logic-voltage-translation/buffers-drivers-transceivers/inverting/products.html#116=Open-collector%3BOpen-drain&480=2%3B3%3B4%3B6%3B8%3B12&2192=Partial%20power%20down%20(Ioff)&0min=0.8%3B3.3&0max=3.3%3B18&1994max=20%3B64&sort=1130;asc&

14:18 <zmatt> (the transistor approach would be an inverting open-drain buffer)

15:14 <mattb0ne> thanks for the info zmat

15:14 <mattb0ne> you know when I was trying it out yesterday, it was not giving me 5V

15:14 <mattb0ne> maybe this is why

18:03 <mattb00ne> @zmatt: I am going to buy this

18:03 <mattb00ne> https://digilent.com/reference/pmod/pmodoc1/reference-manual?redirect=1

18:03 <mattb00ne> what do you think

18:03 <mattb00ne> I think that fits the bill and they have it in a module format so less soldering for me =)

18:41 <mattb00ne> question for the peanut gallery

18:44 <mattb00ne> in my PRU deep dive, there was a lot of talk of registers in paticular R30 and R31 which are input and output registers. My question revolves around how C knows what registers are exposed. For example the code snippet I used has defines R30 as volatile register. How does C map that to something meaningful on the beagle? is that handled by the compiler? So if I made something up like R69, would it fail?

19:09 <zmatt> mattb00ne: yes it would fail, the only global register declarations allowed are __R30 and __R31, these special cases are recognized by the compiler. See section 5.7.2 "Global Register Variables" in the compiler user's guide ( https://www.ti.com/lit/ug/spruhv7c/spruhv7c.pdf )

19:10 <mattb00ne> ok thanks

19:11 <zmatt> R30 is essentially a normal register except it also controls external logic, by default it directly controls pru's direct gpio outputs (when configured into that mode at the SoC-level)

19:12 <zmatt> R31 is not a normal register, reading it will read special inputs to the PRU code, writing to it is used to trigger events / issue commands to external logic