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 Post subject: PIC18F44K22 help
PostPosted: 22 Sep 2012 19:22 
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I'm making my first circuit with Eagle, I'm using a PIC18F44K22, I'd made the symbol myself from the datasheet, when I error check the circuit I get two errors:

Unconnected INPUT pin IC1 RA7/OSC1/CLKI
Unconnected INPUT pin RE3/!MCLR!/VPP

The '!' around the MCLR simply put a bar over the text when showing in the graphical editor. I've read the MCLR when not used to reset should be connected to VDD, is this correct?

But I'm not sure what to do with RA7, I'm using the internal 8Mhz clock.

Thank you for any help.

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 23 Sep 2012 19:57 
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Think of it like the compiler 'Hints' where Eagle is saying: "pin XXX is not connected is this an omission or intentional?"

I would connect !MCLR to VDD via a 10k resistor with a pcb mount push button switch to VSS. This gives you a manual reset.

Unused pins should ether be left open circuit and set as an output or connected to either VDD or VSS and left as an input (reset default).

What about connecting the function you presently have connected to RA6 to RA7. The micro can be configured to output the oscillator on RA6 'CLKO' allowing you to measure the actual oscillator frequency with a 'scope or frequency counter.

Keep the accuracy of the internal oscillator in mind: Internal Calibrated HFINTOSC Frequency +/- 2% 16.0MHz 0°C to +60°C, VDD >=2.5V if you are using higher baud rates, frequency counter etc

Also, Note 1: To ensure these oscillator frequency tolerances, VDD and VSS must be capacitively decoupled as close to the device as possible. 0.1 uF and 0.01 uF values in parallel are recommended. A 10uF cap as well can't hurt.

Have you read the Errata for this part, only 6 items listed and I must say Microchip are improving as there were 36 items listed for the PIC18F8722 when I used it a few years ago :evil:

Hope this helps :D


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 Post subject: Re: PIC18F44K22 help
PostPosted: 23 Sep 2012 21:23 
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Location: UK
Thank you, I will look into it.

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 25 Sep 2012 18:16 
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Location: UK
Its been suggested that I add a header to my circuit so that the PIC can be programmed on the board. What pins would I need to bring out to the header, I program the EasyPic v7 via the serial port D-Type connector. I plan to use the 44-pin TQFP package of the PIC18F(L)F4XK22.

I've looked at the EasyPic v7 schematic, but its not clear to me what I need to do...electronics isn't really my thing, still learning.

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 25 Sep 2012 19:33 
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Have a look at pages 16-19 of the mikroProg User Manual http://www.mikroe.com/downloads/get/1683/mikroprog_pic_manual_v220.pdf Allows programming and ICD using a 0.1" DIL header.


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 Post subject: Re: PIC18F44K22 help
PostPosted: 25 Sep 2012 21:21 
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Location: UK
Thank you, very useful, might be a silly question, but are the yellow, red and green symbols on the diagram on page 17 LEDs?

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 25 Sep 2012 21:54 
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Yes they are LEDs but you don't have to have LEDs on these lines. The point mE may be trying to illustrate is that no components which will present any load should be connected to !MCLR, PGC or PGD during programing.

mikroProg has a mutiplexor, see page 18, which disconnects any loading components during programing - assuming the user circuit has been designed correctly according to the mE microProg documentation.


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 Post subject: Re: PIC18F44K22 help
PostPosted: 26 Sep 2012 20:04 
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Location: UK
Almost there....only 1 Error remaining, for some reason it complains:

Unconnected INPUT ping IC1 RA7/OSC1/CLK1

I don't have anything connected to RA7, I'm using the internal clock, so why?

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 26 Sep 2012 20:39 
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Joined: 12 May 2007 13:01
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Location: DURBAN
Quote:
I don't have anything connected to RA7

Eagle is saying: "pin RA7/OSC1/CLK1 is not connected is this an omission or intentional?" In your case it is intentional so ignore the error or change the package and make RA7 NC if you want Eagle to report no errors.


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 Post subject: Re: PIC18F44K22 help
PostPosted: 26 Sep 2012 21:00 
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Ty will do !

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 29 Sep 2012 08:51 
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Is it necessary to connect pins 6 and 29 (VSS) together and pins 7 and 28 (VDD) together on the PIC18F44K22 TQFP package?

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 29 Sep 2012 09:08 
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Joined: 05 Mar 2009 10:28
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sy you need to connect all VSS pins to ground and allVDD pins to the positive rail and make sure you use decoupling caps at the VDD pins

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 Post subject: Re: PIC18F44K22 help
PostPosted: 29 Sep 2012 18:00 
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Thank you, my circuit will be powered by a battery (5v). What size capacitors should I use? Sorry, I tried searching using Google but couldn't find a decent response.

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 30 Sep 2012 08:51 
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Location: UK
I have decoupling capacitors around the regulator that is connected to the battery, is this enough?

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Sy


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 Post subject: Re: PIC18F44K22 help
PostPosted: 30 Sep 2012 09:47 
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Joined: 12 May 2007 13:01
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Usually the regulator manufacturer will specify the value of capacitors that should be connected to the input and output of the regulator.

If you post the circuit diagram for the regulator, plus max. battery voltage (fully charged), min. battery voltage (fully discharged) and micro supply voltage forum members will be able to give you more complete advice.

Secondly, what is the expected current required by your circuit - regulator heatsink considerations, will it be fairly constant or will you be turning on/off high current loads for example multiplexed LED display ?


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