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ISPnano - Atmel AVR On-Chip Oscillator Calibration - Run-Time License |
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The Equinox 'AVR Oscillator Calibration Firmware' provides a fast and accurate method to calibrate the internal RC oscillator of most Atmel AVR microcontrollers. The majority of the present AVR microcontrollers offer the possibility to run from an internal RC oscillator. The internal RC oscillator frequency can be calibrated to within +/-1% of the frequency specified in the datasheet for the device. This feature offers great flexibility and significant cost savings for AVR designs compared to using an external oscillator. Equinox have developed our own 'RC Oscillator Calibration' algorithm which can be used with our PPM3-MK2, PPM4-MK1 or ISPnano Production ISP programmers. This firmware finds the best-fit 'Calibration value' within user-specified limits (e.g. +/-1%) by checking all OSCAL values until the optimum value is found. The algorithm is compatible with both the SPI and JTAG programming interfaces.
The Development Pack (UPG11M) includes the Calibration Firmware Hex file for the required microcontroller plus technical support to get you up-and-running. Any subsequent programmers only require the Run-Time license (UPG11A). |
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Calibration Firmware Features |
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- Calibration Procedure is compatible with the AVR SPI Programming Interface
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Calibration Procedure is compatible with the AVR JTAG Programming Interface
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Algorithm finds the best-fit 'Calibration value' by checking all OSCAL values until the optimum value is found
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Selects best-fit OSCAL value even if there are overlapping OSCAL frequency ranges
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Starts at the lowest frequency first and then works upwards so the AVR device is always kept within its 'Frequency Specification'
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Possibly slower than Atmel AVR055 algorithm but calibration accuracy is usually better
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Accuracy of Oscillator Calibration is usually within +/- 1%
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Programmer uses accurate 32.768 kHz oscillator for the Calibration Procedure
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Best-fit OSCAL value is stored in a specified address in the AVR EEPROM
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Diagnostics including the '% accuracy' and 'number of iterations to reach the optimum OSCAL value' can also be stored in the EEPROM
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Calibration using the SPI Interface |
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- Accurate 32.768 kHz signal is output from the SPI MOSI pin under programmer control during the Calibration Procedure.
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The PASS / FAIL result of the Calibration Firmware is indicated by the AVR Microcontroller asserting the MISO pin back to the programmer.
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The AVR RESET pin must be used in SPI mode to start the Calibration Procedure.
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The SPI Interface can be used for SPI In-System Programming when not being used for the Calibration Procedure.
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Calibration using the JTAG Interface |
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- Accurate 32.768 kHz signal is output from the JTAG TDI pin under programmer control during the Calibration Procedure.
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The PASS / FAIL result of the Calibration Firmware is indicated by the AVR Microcontroller asserting the TDO pin back to the programmer.
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The AVR RESET pin must be used in JTAG mode to start the Calibration Procedure.
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If control of the RESET pin by the programmer in JTAG mode is not possible then a custom version of the 'Calibration Firmware' is required.
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The JTAG Interface can be used for JTAG In-System Programming when not being used for the Calibration Procedure.
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For further information about related products, please see the Overview Product.
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