The code runs, and the debug lines print, but the LEDs have never lit up.
I then wired up a USB A plug and cable to the VCC and GND on the Glowbit, snd plugged in to USB power supply in case the power was not enough to light up the LEDs.
Hi David
Don’t know much about RPi or Glowbit but you seem to have 2 separate Vcc connected. I don’t think that would be very advisable. Maybe disconnect the one going to the Pi and make sure the one going to the USB connector is plugging into a supply with enough grunt to power the LEDs
Cheers Bob
PS Leave both the grounds connected
|I tried that too, just the Power from the home made USB cable, plugged in to a battery pack capable of over 2 amp, and the white cable plugged into GPIO 18, and black into the Ground on the Pico.
I did notice that when I plugged in the home made usb power plug into the power pack, the glowbit flashed green super briely. I had not seen that before, but TBH, it was always in a bright room with the LEDs faced down to the desk when I did the initial USB plug in previously.
It seems so close. Hoping I can figure this out with some help.
Also, I put the usb power supply into the always-on mode for these tests. If no power drain, it will normally stop supplying power, but I can confirm 5 volts at the glowbit vcc and gnd during my tests.
I tried to specify the exact GPIO pin, and swapped through GPIO 18 and GPIO 20. also tried specifying a low brightness. Still no demo showing.
This feels close.
How is the pico being powered? USB?
@Robert93820 if the pico is powered by the usb and the pico has a commons with the battery pack does that battery pack have a common ground with the USB?
My intuition says that there would be a common ground but two return paths, the earth and the battery. And because the battery isn’t connected to earth (directly) both return paths should be willing to accept the all the current flowing. I even wonder if it would prefer one over the other. Could you clarify?
@David148064 Is there any reason you can’t power the pico off the battery pack too?
I am still connecting the pico to the Pi 3b+ running Thonny. The pico is plugged in to a powered usb hub, with its own 600 mA power supply. So i assume in this case, the power vcc and ground are connected to the usb hub power supply, and the data lines from the pico usb plug are going to the pi 3b+. To switch it to only the power pack, i need to remove Thonny from the mix. I don’t know yet how to load the program onto the pico and run it standalone. I was just doing this first test, following the guide in the Core Electronics YT and written guide.
TBH, the power from the second power source is likely confusing the matter more than it needs to be. I only added that after hours of testing trying to get the unit working directly from the pi 3b+ directly, then from the powered usb hub with 600 mA power supply and the pi 3b+. It really should be able to work without the second source of 5v for the purposes of this test (according to the Core Electronics guide). 600 mA power should be able to at least get 1/3 of the brightness of the glowbit given that the hub only has to power that glowbit and a bluetooth keyboard dongle.
I had tried specifying the pin in case something was wrong there, and i tried setting the brightness to a lot of different low levels to attempt to make sure it was low enough to not be a power issue, and still be high enough to see.
I don’t know if i am missing something that is not in the instructions, or if i have some unforseen incompatibility, or if my glowbit is faulty.
Connect the Data (White???) and Ground (Negative black) to the RPi.
Connect the external 5V to Glowbit Pos and Glowbit Neg (via home made USB connector)
This will provide external 5V for the LED supply. The ground connection between Glowbit Ground and RPi is to provide a ground return for the control data back to the RPi.
You can still connect Thonny and power the RPi via the USB port without any changes.
I think the way you had it in the Pic you are effectively connecting 2 separate lots of 5V to RPi and I am not sure the RPi likes that very much. As a general rule I don’t think this is advisable.
Cheers Bob.
The Pi 3b+ has a 5 volt 5 amp power supply. That is powering a Pi3b+ and a 7 inch colour display.
I have a powered USB hub. It has its own 600 mA 5 volt power supply, as I did not think the power supply for the 3b+ had enough to drive the pi 3b+, the display, the pico, and the Glowbit. I believe that a powered hub actually isolates the vcc and ground from the Pi 3b+. VCC and Ground must be coming only from the hub power supply??
Optionally, I can plug in the other home made USB cable that I soldered to the glowbit. I can plug this in to the hub itself, or to any other power supply. I have only done this as a test, just because the doco stated that there could be a power supply issue if running glowbit at max brightnes. I am keeping the glowbit at minimal brightness, so this really is not needed at this point, and remains unplugged for now.
The powered hub is pictured below… I purchased this a long time ago. I am fairly certain that someone recommended this in my earliest Pi3b+ project, specifically because it completely offloads all power needs for all peripherals away from the Pi3b+, which can have power issues with minimal items connected.
It is my belief that the hub eliminates the pi3b+ power from the equation in terms of the Pico and the glowbit power supply. And the third power supply was only utilised once, just to test that as an option. It is no longer being used. Eventually, once the glowbit is working, I may re-engage that as a higher amp power option, without the red vcc cable connected to the pico.
Below is a picture of the inside of that hub. I am not sure if that tells the story of the 5v routing. It either has to terminate the 5v from the pi 3b+, and use only the connected power supply, or join it with the power supply from the usb hub…
One thing is for sure. If you are powering the RPi from somewhere else do not connect that red wire between RPi and Glowbit. That is only used if you are powering Glowbit from the RPi which I very much doubt it will do.
The powered hub should pass the ground connection through. If powered it should isolate Vcc positive from the parent device (PC or whatever) to prevent 5V back feeding. If the hub is UNPOWERED it should pass yje 5V Vcc from the parent device to the outputs. The Ground pass through is required for any data circuits to be maintained.
Comment: 600mA is not really much so I would not depend on that to power anything significant like a bunch of LEDs. The current capability should be a function of whatever power supply you have plugged into it. If you want a bit more plug in a bigger supply. There might be a connector limit but it shoaled handle anything within USB spec.
Cheers Bob
The very first time I ran this, I followed exactly the steps in the video.
Pi 3b+ connected directly to the pico via usb micro cable, and glowbit connected to the pico with vcc, ground, and GPIO18 data. No other power supplies, hubs, cables. I never got the glowbit to light up. I only added the hub, and then eventually the other usb power supply just to test if it was a power issue.
I just went back to that setup, and still nothing from the lights.
According to the core electronics notes, it should be ok with minimal brightness set, which is what I am trying. At max brightness, they say it drawas about 2 Amps. At 10% brightness, it should draw approximately 200 mA, which should not be an issue.
Hi David
I haven’t got the time just now to watch all of that video.
The impression I got with what I did look at was this could be driven by Pico OR RPi (3b???) NOT both.
This suggests you have both connected in series. Not sure why that would work. Just because you get the correct messages on your PC screen does not mean the correct data is getting to the destination. Only that is leaving THIS PARTICULAR device correctly on the nominated pin.
I don’t quite see how using 2 devices in series is going to work.
My suggestion here is to try either a Pico or RPi, NOT both.
Will try to get a look at the rest of the video when my visitors leave.
Cheers Bob
To avoid confuction can you clarify which USB connects where, the Pico should be connected to your Pi 3. What is powering you matrix at the moment? Your Pi won’t be able to match the current requirements of your LEDs so you will need another source.
I have tried everything from a 3 amp 5 volt usb wall wort to a 5 volt 3 amp usb battery bank, both directly into the home made usb cable directly onto the glowbit, to a powered usb hub, to directly running off the raspberry pi 3b+ as shown in the video.
I also tried setting the brigtness of the glowbit down to 5%, 10%, 15%, etc to see if less brightness shows up, requiring less power.
Just now I tried this, which should be the simplest setup:
I then wrote a simple python code to flash the LED on the PicoW every second, saved it to main.py on the pico, un-plugged the Pico from the Pi 3b+, plugged the Pico into a battery bank, and the pico started flashing the LED at 1 time per second. This should prove that The pico can receive the pain.py and execute it when it is turned on.
I then loaded the glowbit library to the PicW as the re-flashing had wiped it.
I then replaced the main.py on the pico with this code:
Connected vcc, ground and data pin from Glowbit to Pico
Plugged the Glowbit in to a battery bank to get 5v power
Plugged Pico into battery bank to boot it up.
No lights on Glowbit.
This is the wiring. Confirmed with a multimeter that there is 5v on the two wires into the Glowbit, and 5v on the two wires to the pico. That battery pack is capable of over 2 amps.
Hi David
I think I am slowly getting to realise what is going on here.
A couple of things would have helped out and prevented incorrect guesswork.
You have not yet provided a circuit or sketch of exactly what you have connected to what and how is all this arranged.
On no picture do you show your RPi 3b or how it is connected.
I realise now after
that you could be using the RPi as a computer to program the Pico.
Is that the case???
I have been assuming that you have been using a Laptop or Desktop PC to do the programming and the 2 RP devices were somehow connected in series.
Hi Davis
I Have just noticed this (replies crossed over)
Yes. You still have the 5V connection from the Pico and power bank connected.
I did say
Don’t you read and take note of replies?
If you are using that Pico connection to power the Pico, that is 5V input to the Pico, and not using USB for this it is possible that 5V IN on the Pico is a different pin from the 5V OUT pin. If this is the case the Pico might not be getting any power when you remove the USB cable.
Cheers Bob
Cheers Bob
It would appear (to me anyway) that if you want 5V OUT of the Pico you would connect to “VBUS” and that would give you a direct connection to the 5V as supplied by the USB input with the USB supply current limitations.
If you are supplying the Pico with 5V externally, that is 5V IN to the Pico you should I think connect the external supply to “VSYS”. Then the diode D1 prevents this 5V back feeding up the USB cable.
Now not being familiar with RPi I don’t know what effect this would have. It might not be good. It is recommended you never allow this to happen.
With your set up you seem to have the Pico connected from Glowbit + which is connected to power bank to VBUS at all times. If connected to power bank you should be connected to VSYS.
As I think I said before you power the Pico with the same LED external 5V OR USB but NOT both. By connecting as you show you are powering Pico from BOTH which could have unknown implications.
I think before you go any further you should connect properly. I think the external supply for the LEDs is a good idea but make sure that power bank is not shutting down at low current drain.
If you want to power the Pico from this connect it to VSYS. If you want to power Pico from USB then disconnect it from the LED supply completely.
Then see what happens. The way you seem to be playing swappsies in what seems like a random fashion could mean you are going in circles forever.
Cheers Bob
I will check this out later. My initial setup is identical to the guide that Core Electronics have in their video and their written instructions. The expanding list of other connection options only came about because that did not work. I think I have exhausted all possibilities, and am running out of time to spend on it. It is a pitty, because it was an expensive little display, and I think it is just going to be landfill. I really wanted that for a feedback mechnism. Unsure if I want to waste further time on this Glowbit, as it is just not working. I have proven multiple times in my testing that the pico is fine, it works, just the Glowbit refuses to light up.
