[closed] Big array issue ???

spilz · Joined: 30 Jan 2012 Posts: 220

It's 10:35 PM here, so I'm not working on it until tomorrow ^^

You have the same issue ?
I mean you are able to reproduce my issue ?

thanks for your help

temtronic · Posted: Tue Dec 06, 2016 5:09 pm

two comments..

1) get rid of the 'restart_wdt', etc. disable the WDT. You never need that until the product is ready to go out the door.....

2) have a look at the 'software RTC in the code library. Using that code it is dead simple to have an 'event' happen after 7 seconds. In fact I've used it in a few projects,triggering several events.

Jay

spilz · Joined: 30 Jan 2012 Posts: 220

Thanks for your reply, I'm agree with you.
My code does not work as simple, it's to show the issue when create a big array.

I still not understand this issue, and it's good to know if we can't use big array without unexpected issue :(

Ttelmah · Joined: 11 Mar 2010 Posts: 20059

What sort of LED?. For a red LED, Vf is typically only about 1.8v. Pin D4 is only rated to deliver 8mA. With 3.3v as power, the LED will be drawing nearly 15mA. Twice what the port is rated to give. These chips only have low power delivery on many of the pins.

I've just run the code up on a board I have here with the QFN 47J53, and with a 300R resistor, it is blinking the LED every 7 seconds reliably. However the fuses were those for my chip (8MHz external oscillator).

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I tested it with vs. 5.064 and an 18F27J53, and with the enable/disable
interrupts code. It worked with or without the array declaration.
It did a short blink about every 7 seconds. However, since this PIC
is not your exact PIC, it's not a complete test.

spilz · Joined: 30 Jan 2012 Posts: 220

@ Ttelmah :

- I use SMD led, datasheet says 2.1/2.3V, so OK, my resistor is a little low, I will change it to a 300R.

- thanks for your explanation about WDT, I didn't know that and it was something I wanted to work on.

- about Vcore, I just connect it to ground with a 10uF. It's what I understand from the datasheet for 'F' :

spilz · Joined: 30 Jan 2012 Posts: 220

Ttelmah · Joined: 11 Mar 2010 Posts: 20059

Do you have an external oscillator, or a crystal?.

spilz · Joined: 30 Jan 2012 Posts: 220

my mistake, I use a Crystal one

what about Vddcore/Vcap ?

Ttelmah · Joined: 11 Mar 2010 Posts: 20059

Your code shows you have an F device, not an LF. On the F, Vddcore is the output from the internal regulator. It needs really good smoothing, but nothing else. Key though is that it must have very good ESR performance. This is why they list the suitable types. A 'generic' capacitor on here will almost certainly give problems.
On the board I was using, there are actually five capacitors within 10mm of the chip. The 10uF Vcore capacitor, one 1uF on Vusb. two 0.1uF ones where the supply comes into the chip on opposite sides, another 10uF on the feed providing this, and inductor and 10uF capacitor on Avreg. There is a switched mode regulator that provides 5v, and this feeds a MIC29302, that gives the 3.3v supply.

The point is that it is too 'coincidental', that you started posting with problems on USB, and are now having other 'inexplicable' problems on much simpler code, using the same chip. I have to suspect there is a hardware fault. These chips are much less forgiving than the older simpler PIC's (where you could often run them off awful supplies). They need really good smooth supplies with lots of care in the layout.

spilz · Joined: 30 Jan 2012 Posts: 220

actually it's 2 parts of the same project, on the same board

I'm starting to use these chip, so an hardware issue is possible, but I'm surprised by the fact that just declare a varialbe without using it change so much like this ...

- I didn't connect Vdd2, I will do it and add a 100nF close to it.

- I'm using 470nF to Vusb, is it a problem ?

- I will change the 10uF Vcap, but I only have 100uF low ESR now, is it a big problem ?

I'm using 44-Pin TQFP, I don't see 'Avreg'

Ttelmah · Joined: 11 Mar 2010 Posts: 20059

You _must_ connect all the power pins. It's very probable that Vdd2, is actually the one feeding the RAM. Could explain a huge amount. The power connections are there because they are _needed_. Manufacturers don't waste pins. They are there to ensure a well decoupled low impedance supply to different parts of the silicon die...

Look at this thread:

<http://electronics.stackexchange.com/questions/22662/if-a-pic-mcu-provides-multiple-vdd-vss-should-you-provide-power-to-them-all>

When you add the big array, you change _where_ the other variables are stored. If part of the RAM is not properly powered, result garbage....

spilz · Joined: 30 Jan 2012 Posts: 220

I connected Vdd2 to 3.3v, with a 0.1uF connected to Vss2 (Vss2 is connected to ground)

I changed the 10uF (Vcap) to one with low ESR (given by a friend)

I added 10uF on close to the power supply

I changed the resistor to a 300R

-> still have the issue :(

spilz · Joined: 30 Jan 2012 Posts: 220

OK,

stop searching, I'm using a USB bootloader to load my program, and without using it, it works well, so I think the issue is from the bootloader.

As the USB Bootloader works for other programs without issue, I didn't think about it.

Thanks for your help and the time you spend for me, it was not usefull, I learn a lot with you Smile

I will open a new thread about bootloader

Spilz