Just how to Correct a System32 Config Starting Mistake - And How to Reduce it From Coming Straight back

 Microcontrollers are generally dedicated to a specific function, therefore while they're very variable units these days, you will find a number of different (often conflicting) choices for how you could want the electronics to work. You may think that setting is completed in application, but what if you prefer the hardware to act a particular way from ab muscles begin? Bearing in mind that Microchip PIC products may "boot" in a matter of milliseconds, there wants to become a way you telling the electronics just how to act before it starting up. This article covers how to really get your microcontroller centered project functioning the manner in which you assume when it begins up.

Enter config pieces, or, because they was once called, openbullet config. Back the occasions when microcontrollers were program-once units, you actually did blow a fuse to be able to plan them. Nowadays, many micros have flash memory which can be set countless amounts of occasions, but there are still one-time-programmable (OTP) products about.

Regardless, there's a lot of "config words" that determine how the micro will behave from the get-go. Let's search at some of these alternatives (we'll choose the PIC18F2620 being an example) and then see how to program them. Sourceboost provides you with most of the config strings in a ready-to-use format for including in your project. The structure has got the config pieces suffixed with exactly the same title while the config word in order to make certain that the proper bits are getting in the proper word. Of course, your config phrases is likely to be different if you're employing a various microcontroller, but you must understand enough here to place you in the best direction.

In the 18F2620, the config pieces are stored in thumb, but at a high storage location. They're kept at 0x300001 and upwards. For old factors due to the way memory was once fixed on PIC microcontrollers, config phrases are numbered with each quantity having a "high" and "low" byte.

CONFIG1L doesn't exist on the 18F2620. If it did, it would live at 0x300000 location.

CONFIG1H contains bits that establish oscillator options. Usually, in Embedded Ventures projects we try and use outside deposits which give more accurate and trusted results. That does consume two pins however, and sometimes these could become more crucial compared to the rate at that your chip is running. The outside gem oscillator is called the HS oscillator (if you're doing the normal thing of trying to run the micro as rapidly since it may go). In the 18F2620, you can even permit the PLL module which will give you a four-times speed boost. From CONFIG1H may also be possibilities allow the fail-safe time check (that turns to the inner oscillator if the additional one crash, and an alternative allow the switching between different oscillator sources.

We usually recommend that you use an additional crystal, and turn fully off any oscillator converting / failover modes. In prototyping, it is very important to have trusted, repeatable benefits (mostly to help you reduce the axes of error). It's possible to configure the 18F2620 to start up utilizing the internal oscillator (which runs at 8Mhz, or 32Mhz with the PLL enabled) and then switch to the additional one (we use a 10Mhz crystal with PLL permitted providing you 40Mhz). That offers you faster startup from stops in sleep mode or on bootup, if that's important, except for prototyping, this really is generally maybe not necessary.

Our encouraged config sequence for CONFIG1H:

#pragma DATA _CONFIG1H, _OSC_HSPLL_1H & _IESO_OFF_1H & _FCMEN_OFF_1H

CONFIG2L grips brown-out reset and the energy up timer. Brown Out Reset (or BOR) is the ability for the microcontroller to reset it self if the present voltage falls below a given threshold. It'll stay static in reset state before the supply extends back over the threshold. This could suggest some battery preserving (at least, when the battery is smooth beyond a certain level, it'll stop wearing power as quickly) - but at that time there's number operation accessible anyway. The power on timer waits on preliminary power-on for the present to move above the BOR voltage ceiling, then weighs around for yet another 65ms before kicking points down for real. This assists assure that your power supply is constant before trying to execute any code.

We've observed some very unknown effects from the 18F2620 when testing some LED present panels. We believed the application was crashing or resetting the micro when in fact, what was happening was the BOR had been tripped as more LEDs were lit and the power present dropped. As such, until you've got a real need for it, we recommend switching it off. Causing the ability source to stay before starting the firmware, is generally advisable (you're probably not planning to notice the 65ms it takes).

#pragma DATA _CONFIG2L, _BOREN_OFF_2L & _BORV_2_2L & _PWRT_ON_2L

CONFIG2H provides you with controls for the watchdog timer. This is a timer that resets the PIC in a quantity of time (you may extensively establish just how long that will be). It might be excellent want to reset your PIC if you're doing something from that you simply may never retrieve - although ideally you're published good enough signal that this can't occur! As an alternative, the watchdog timer may also move the PIC out of rest mode. This implies you are able to arrange for the PIC to get to sleep for a specific amount of time (if nothing else happens). For prototyping, we recommend changing the watchdog timer off. If you do help it, make sure you reset the watchdog timer regularly or - well, you can guess what'll happen.

#pragma DATA _CONFIG2H, _WDT_OFF_2H & _WDTPS_128_2H

CONFIG3H has an accumulation configuration items. You are able to pick for the RE3 green to be around (as input only) and for that pin to be MCLR (which resets the micro when drawn low). For prototyping, to be able to reset the micro by pushing a key is easier than dragging the power out.

The LPT1OSC bit provides the option of a "large power" style or even a "minimal power mode" ;.The reduced energy setting is more painful and sensitive in large sound environments. So if battery consumption is vital, you'll need to design your enterprise carefully. For prototyping, obviously, we would recommend leaving that in high power mode.

PBABEN, allows you to specify if PORTB pins 0 - 4 must get up as analog insight pins or digital pins upon reset. Needless to say you are able to change that in computer software in the ADCON1 enroll at any time.

The CCP component is just a Capture / Examine / PWM module and your final CONFIG3H bit allows the "steering" of the productivity to be on sometimes RC1 or RB3. This is practical to be able to change in the event that you need the other operation on one of these brilliant hooks (RB3 can also be analogue insight 9 and RC1 can be Timer 1 oscillator input). As an alternative, your PCB structure could be easier if you might move this result to at least one or the other. For prototyping, usually that doesn't matter often way.

#pragma DATA _CONFIG3H, _CCP2MX_PORTC_3H & _PBADEN_OFF_3H & _MCLRE_ON_3H

CONFIG4L contains some interesting alternatives and shows very clearly how crucial it is to manage to configure the PIC before startup.

The DEBUG touch enables equipment debugging. You are able to stage through signal, set breakpoints and so on - when you yourself have your computer software collection effectively and this touch cleared. Equipment debugging also involves the unique use of RB6 and RB7 (also used for ICSP programming). In all credibility, we discover that serial productivity is usually sufficient to locate bugs, even though you are able to debug plenty of PICs with merely a PicKit2.

XINST makes for the 18F extensive training collection mode. This isn't utilized by Sourceboost and in the event that you change it on by mistake (regardless of the compiler you're using) you will have some pretty unknown results. Certainly one of our visitors used days trying to find that which was improper with his rule simply to understand the XINST bit was set.

LVP provides you with the ability to plan the PIC applying ICSP without requiring the "higher" Vpp voltage. There's a catch nevertheless - you will need to devote the RB5 green (PGM) to being an indicator if you're in programming method or not. Provided the PicKit2 produces the right voltage anyhow, there doesn't be seemingly a lot of value in converting this on for prototyping purposes.

Ultimately, the STVREN provides the possibility of getting the PIC reset if the stack overflowed or underflowed. If, like, you call a lot of stacked features, it allows the PIC to reset. Once reset, you can study why the PIC reset and record a fault. We suggest leaving this on - if your PIC boots in the midst of performing something, you are able to fairly believe that you've consumed the heap space (possible when you're strong in a nested situation and then an disrupt occurs).