jreebel
Posts: 4
Joined: Sun Jan 26, 2020 11:25 pm

Inconsistent results with Freenove kit

Tue Jan 28, 2020 4:34 pm

I'm new to the Pi, just got a 4B for Christmas, then purchased the Freenove Ultimate Starter Kit. My relevant background is 35 years of professional programming experience in various languages (now learning Python), some usage of Unix and nothing about electronics although lots of DIY experience with electricity (rewired my garage, added circuits, etc.).

My problem is the results I'm getting trying to work with this kit. Whenever I reach the point where I think the basics are starting to make sense things immediately go south. I have set up various circuits to make an LED blink based on Youtube tutorials and the tutorial from the kit. Some worked, some didn't. My latest experience has me completely frustrated and I'm hoping somebody here can tell me what I'm doing wrong or suggest some new approach.

I set up a very simple circuit to blink an LED. Just the LED, a resistor, jumpers to ground and GPIO 04, and a bit of simple Python code. It worked. The next morning I ran it again. Still worked. I moved one of the jumpers from the ground to the negative rail on the breadboard and added a jumper from the ground to the negative rail. Didn't work. Went back to the original setup. Didn't work. Aaargh! If I move the jumper from GPIO 04 to the 3.3 v pin the LED lights up, so the circuit must be OK, right? Put it back on GPIO 04 and the (unchanged) program doesn't work. I've attached a pic of the setup. Any thoughts? Please, before I run screaming down the street.
IMG_1510(1).jpg
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richrussell
Posts: 28
Joined: Thu Jan 16, 2020 10:52 am

Re: Inconsistent results with Freenove kit

Wed Jan 29, 2020 9:34 am

I assume you're doing this on breadboard (supplied with the Freenove component kit maybe)? It sounds like an issue with how you're placing the wire links and components on that rather than an issue with the Pi hardware or python code.

If so - could you post a photo of your setup? Some breadboards have a break in the middle of the positive/negative rails, so if your connecting on either side of the gap, you won't get a connection.

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B.Goode
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Re: Inconsistent results with Freenove kit

Wed Jan 29, 2020 10:07 am

richrussell wrote:
Wed Jan 29, 2020 9:34 am
I assume you're doing this on breadboard (supplied with the Freenove component kit maybe)? It sounds like an issue with how you're placing the wire links and components on that rather than an issue with the Pi hardware or python code.

If so - could you post a photo of your setup? Some breadboards have a break in the middle of the positive/negative rails, so if your connecting on either side of the gap, you won't get a connection.


To reinforce the suggestion already made, that you may have a 'broken' (by design) ground rail on the breadboard.

Documented as a well-known issue here: https://www.raspberrypi.org/forums/view ... 14#p635787

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neilgl
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Re: Inconsistent results with Freenove kit

Wed Jan 29, 2020 10:36 am

We can’t see the photo

jreebel
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Joined: Sun Jan 26, 2020 11:25 pm

Re: Inconsistent results with Freenove kit

Sun Apr 05, 2020 7:55 pm

Sorry I didn't respond with a photo - was unaware anyone responded. I solved that issue by buying a better breadboard and that solved the problem. Now I've reached a project with lots of connections and an i2c chip which isn't working. I've no idea how to approach this to find where the problem is. Any easy way to test the PCF8591 chip itself to start with?
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richrussell
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Re: Inconsistent results with Freenove kit

Mon Apr 06, 2020 11:03 am

Is that the A/D converter tutorial (read the value of a potentiometer) - Chapter 7 (it is in the PDF I have, which might be older than yours)?

If so, make sure you have got I2C enable in raspi-config as it shows in the tutorial, and do the test to see if the PCF8591 is detected on the I2C bus.

jreebel
Posts: 4
Joined: Sun Jan 26, 2020 11:25 pm

Re: Inconsistent results with Freenove kit

Mon Apr 06, 2020 10:27 pm

Yes, that's the one. I did all the configuration but nothing shows up on that test but dots, looks like it doesn't see the chip. Is just having the chip on the board enough to make the test valid, or do I have to connect it to something?
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richrussell
Posts: 28
Joined: Thu Jan 16, 2020 10:52 am

Re: Inconsistent results with Freenove kit

Tue Apr 07, 2020 11:10 am

It will need at least the power pins (Vdd and Vss) as well as the I2C pins (SCL, SCD) and the hardware address pins (A0, A1, A2) pins connecting up as shown in the diagram in the tutorial to communicate with the Raspberry Pi. That's pins 5, 6, 7, 8, 9, 10 and 16. Also you'll need the 10k pullup resistors on SCL and SCD.

If you've done those, you might as well do the rest of the circuit - pins 1, 12, 13, 14 and 15 though so it's got an input and output for the code to get the chip to look at. :)
Last edited by richrussell on Tue Apr 07, 2020 11:44 am, edited 1 time in total.

richrussell
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Re: Inconsistent results with Freenove kit

Tue Apr 07, 2020 11:44 am

OK - I've just put the circuit together on breadboard as shown in the tutorial and it worked first time when I ran the python code.

So double check your wiring on the breadboard - if you've got the smaller PCF8591 on a little circuit board you'll find you might need to alter the position of some of the jumper wires as you can't quite get to the holes in the breadboard nearest the pins if you see what I mean ;)

jreebel
Posts: 4
Joined: Sun Jan 26, 2020 11:25 pm

Re: Inconsistent results with Freenove kit

Tue Apr 07, 2020 4:38 pm

OK, I'll set it up again, first with the minimum, and see what happens. I have the larger chip, newer version I guess. Your mention of "close to the pins" has me wondering if I'm confused about something. I've been assuming that anywhere on the row is fine for the jumpers. Are you implying that I need to follow the diagram exactly as to which holes the jumpers go into? Thanks for all your help with this!
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richrussell
Posts: 28
Joined: Thu Jan 16, 2020 10:52 am

Re: Inconsistent results with Freenove kit

Wed Apr 08, 2020 7:57 am

Anywhere on the row is indeed fine, you don't have to follow the diagram exactly - I was just pointing out that you might not be able to follow the diagram if you had the smaller chip on the little pcb because the pcb gets in the way.

I'm sure you're just missing a connection somewhere (perhaps the pullup resistors on the I2C connections?) but otherwise it's corrrect.

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