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March 7, 2011 AT 11:01 am

EVEN MORE Commandments for Using PICs

After seeing our post about Commandments for Using PICs, George Hadley wrote in with even more great tips. He writes:

7. The VDDCore/VDDCap and ENVREG/DISVREG pins must be connected

In addition to some of the other pins, many PIC microcontrollers (particularly the PIC24 and PIC32 product lines) contain pin called VDDCore/VDDCap and ENVREG/DISVREG. These pins are used to enable or disable internal voltage regulators to the core microcontroller logic. Depending on your application, there are a number of possible connections for these pins (Microchip provides a fairly good write-up here), but regardless of your application, these pins should not be left floating.

8. Read the Errata

The good people at Microchip technology work very hard to make low-cost, high-quality microcontrollers. That said, however, production PIC microcontrollers do not always perform to the ideal specification that their datasheets detail. Batches occasionally come off the line in which flaws in the design are discovered later. In these situations, reading the errata before you order your PCB can be a life-saving experience. The errata can be found on the main page for a given microcontroller or device on microchip’s website, and can tip you off to flaws. For an example of what can happen when you don’t read the silicon errata for a microcontroller before moving forward with a design, talk to Dave Jones.

(this video contains some rare footage of Dave getting upset. RARE. srsly.) 😉

9. Do not use an LF part in place of an F part

For most of microchip’s PIC microcontroller product lines, they make 2 variants of a given microcontroller: the PIC18Fxxxxx and the PIC18LFxxxxx. These parts look very similar if you’re scanning a list, but have different functional characteristics. Therefore, it is HIGHLY recommended that you do a quick 2 second check that you have the right part in the shopping cart before you hit that “submit order” button.

[ed. note: the diff. between the “F” and “LF” chips is that “F” chips are designed to run on a nominal 5V supply, while “LF” chips can run at a lower voltage range (say 2-5V)]


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