microcontroller_annoyances
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microcontroller_annoyances [2008/06/10 16:37] pcbgcode High-voltage programming can fix bad fuses too. |
microcontroller_annoyances [2016/01/28 18:05] (current) |
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| ====== AVRs ====== | ====== AVRs ====== | ||
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| ===== Calculating Fuses ===== | ===== Calculating Fuses ===== | ||
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| WinAVR is great, better than AVR studio but there's no nice fuse selector like there is with AVR studio. Luckily there are two calculators | WinAVR is great, better than AVR studio but there's no nice fuse selector like there is with AVR studio. Luckily there are two calculators | ||
| - [[http://www.vonnieda.org/AVRFuses/ | AVRFuses]] is a simple fuse programmer for the AVR series of microcontrollers from Atmel. It is written in C#.NET with the intention of being cross platform compatible with Windows, OS X and Linux. It is written to mimic the look, feel and utility of the AVR Studio fuse programmer. | - [[http://www.vonnieda.org/AVRFuses/ | AVRFuses]] is a simple fuse programmer for the AVR series of microcontrollers from Atmel. It is written in C#.NET with the intention of being cross platform compatible with Windows, OS X and Linux. It is written to mimic the look, feel and utility of the AVR Studio fuse programmer. | ||
| - | - [[http://palmavr.sourceforge.net/cgi-bin/fc.cgi | AVR Fuse Calculator]] is a webpage that does it all | + | - [[http://www.engbedded.com/cgi-bin/fc.cgi/ | AVR Fuse Calculator]] is a webpage that does it all |
| ===== Fixing fuses ===== | ===== Fixing fuses ===== | ||
| Line 56: | Line 57: | ||
| So make sure to always use BOD fuses! | So make sure to always use BOD fuses! | ||
| + | |||
| + | ===== EEPROM corruption from brownouts ===== | ||
| + | Brownouts can cause the first location of the on-board EEPROM to be overwritten. | ||
| + | |||
| + | ''In addition to the precautions elsewhere on this Wiki, consider not using the first EEPROM location.'' | ||
| + | |||
| ===== Brownout fuses ===== | ===== Brownout fuses ===== | ||
| If the voltage on your chip goes too low it can start executing random instructions, or corrupt the flash/eeprom (see above) so just always set the BOD unless there's some good reason not to! | If the voltage on your chip goes too low it can start executing random instructions, or corrupt the flash/eeprom (see above) so just always set the BOD unless there's some good reason not to! | ||
| - | |||
| ===== Reset Pin ===== | ===== Reset Pin ===== | ||
| - | Not really an annoyance, but just so you know: its not necessary to have a pull-up 10K (or whatever) resistor on the Reset pin, there's an internal one already! | + | Not really an annoyance, but just so you know: Unless your design is in an electrically noisy environment, it is not necessary to have a pull-up 10K (or whatever) resistor on the Reset pin, there's an internal one already! |
| - | (Reference: see "DC characteristics" of any AVR datasheet for R_RST 20-100Kohm pull up resisitor) | + | (Reference: see "DC characteristics" of any AVR datasheet for R_RST 20-100Kohm pull up resistor) |
| For a solid design, follow [[http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf|AVR app note AVR040]]'s suggestions: "To achieve the same protection on Reset as on other I/O pins, an external diode should be connected from Reset to VCC. A normal small-signal diode will do //[ed. 1N914 or 1N4148]//. In addition, a pull-up resistor (10K typical) and a small filter capacitor (4.7 nF) should be connected as shown in Figure 4-7." | For a solid design, follow [[http://www.atmel.com/dyn/resources/prod_documents/doc1619.pdf|AVR app note AVR040]]'s suggestions: "To achieve the same protection on Reset as on other I/O pins, an external diode should be connected from Reset to VCC. A normal small-signal diode will do //[ed. 1N914 or 1N4148]//. In addition, a pull-up resistor (10K typical) and a small filter capacitor (4.7 nF) should be connected as shown in Figure 4-7." | ||
| Note: [[http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf|AVR042]] has more info on reset pin design (as well as overall good advice for hardware design w/AVRs) | Note: [[http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf|AVR042]] has more info on reset pin design (as well as overall good advice for hardware design w/AVRs) | ||
| + | |||
| + | If you plan to use debugWIRE, the resistor to VCC should be 10K or larger, and there should not be a capacitor to ground. See page 4 of [[http://www.atmel.com/dyn/resources/prod_documents/doc2521.pdf|AVR042]] for details. | ||
| ===== AVCC ===== | ===== AVCC ===== | ||
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| MOSI -> PE0, MISO -> PE1, SCK -> PB1 // --- //[[http://www.avrfreaks.net/wiki/index.php/Documentation:Things_That_Are_Broken|AVR Wiki]]// | MOSI -> PE0, MISO -> PE1, SCK -> PB1 // --- //[[http://www.avrfreaks.net/wiki/index.php/Documentation:Things_That_Are_Broken|AVR Wiki]]// | ||
| + | ===== SPI Master mode ===== | ||
| + | On some (all?) AVRs, if the SPI slave select (SS_) pin is an input and low, then the SPI interface will go into slave mode, even if you have previously selected master mode. Hope you weren't using that pin for something else. | ||
| ====== PIC ====== | ====== PIC ====== | ||
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