Tsekkaa
AVR EEPROM
Refer Atmel page
EEPROM corruption |
| Question |
|---|
| My EEPROM is sometimes corrupted, what can I do to prevent this? |
| Answer |
| During periods of low VCC, the EEPROM data can be corrupted because the supply voltage is too low for the CPU and the EEPROM to operate properly. These issues are the same as for board level systems using EEPROM, and the same design solutions should be applied. An EEPROM data corruption can be caused by two situations when the voltage is too low. First, a regular write sequence to the EEPROM requires a minimum voltage to operate correctly. Second, the CPU itself can execute instructions incorrectly, if the supply voltage is too low. EEPROM data corruption can easily be avoided by following this design recommendation: Keep the AVR RESET active (low) during periods of insufficient power supply voltage. This can be done by enabling the internal Brown-out Detector (BOD). If the detection level of the internal BOD does not match the needed detection level, an external low VCC Reset Protection circuit can be used. If a reset occurs while a write operation is in progress, the write operation will be completed provided that the power supply voltage is sufficient. What all this means is: If you can't guarantee power, you have to make sure that the part is kept in RESET when it is outside of spec. You can do this using the internal BOD, but this will not take care of the case when an EEPROM write has already began when the part loses power. Thus you must also make sure to write to the EEPROM only when you're sure to have power. It is not enough to write to the EEPROM during "safe periods" and leave the BOD disabled, though: If the part gets outside spec it can begin executing erratically, and the program couter could concievably jump to the part in the code in which the EEPROM is written. These are not bugs but intrinsic demands of the EEPROM. Interrupts are not disabled automatically, but the customer is urged to take care of the following during EEPROM write (the order of steps 3 and 4 is not essential): 1. Wait until EEWE becomes zero. 2. Wait until SPMEN in SPMCR becomes zero. 3. Write new EEPROM address to EEAR (optional). 4. Write new EEPROM data to EEDR (optional). 5. Write a logical one to the EEMWE bit while writing a zero to EEWE in EECR. 6. Within four clock cycles after setting EEMWE, write a logical one to EEWE. Caution: An interrupt between step 5 and step 6 will make the write cycle fail, since the EEPROM Master Write Enable will time-out. If an interrupt routine accessing the EEPROM is interrupting another EEPROM access, the EEAR or EEDR Register will be modified, causing the interrupted EEPROM access to fail. It is recommended to have the Global Interrupt Flag cleared during all the steps to avoid these problems. |
AVR rprint f
https://ccrma.stanford.edu/wiki/AVR_Programming
unsigned int a, b;
unsigned long c = (long)a * (long)b;
minGW
Serial port
http://www.codeguru.com/cpp/i-n/network/serialcommunications/article.php/c2503/
FFT
Näyttömoduuli ja softa:
http://www.arduino.cc/playground/Code/GLCDks0108
http://www.pjrc.com/teensy/td_libs_GLCD.html
LCD modules 128x64
http://www.azdisplays.com/index.php?id=Graphic_Modules&product=g1264f
http://www.e-shore.com.my/homepage/eshop/output-modules/lcd/128x64-dots-graphic-lcd
http://www.newhavendisplay.com/specs/NHD-12864WG-BTMI-VN.pdf
Torsional Vibration
http://blog.prosig.com/2006/01/12/torsional-vibration-tacho-pulses-and-aliasing/
Digital Filters
FIR
http://www-users.cs.york.ac.uk/~fisher/mkfilter/
http://www.bores.com/courses/intro/filters/4_freq.htm
Yleistietoa
http://www.fourier-series.com/f-transform/index.html