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V1.0.1
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felias-fogg committed Jun 27, 2023
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4 changes: 4 additions & 0 deletions changelog.txt
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Expand Up @@ -95,3 +95,7 @@ V0.6.3 (27.07.2023)

V1.0.0 (27.06.2023)
- first public release

V1.0.1 (27.06.2023)
- moved utility folder to extras in order to be compliant with the
Arduino library rules
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// open drain pin using Timer1. Additionally, it passes the 1200 baud output of a target board
// to Serial.

#define VERSION "1.0.0"
#define VERSION "1.0.1"

#define FREQPIN MISO
#define TTYPIN SCK
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// a fully calibrated clock will give us 100000 counts.


#define VERSION "1.0.0"
#define VERSION "1.0.1"

//#define TRUEMILLIVOLT 3309 // the true voltage measured in mV
#define TRUEMILLIVOLT 5003 // the true voltage measured in mV
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2 changes: 1 addition & 1 deletion library.json
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{
"name": "avrCalibrate",
"version": "1.0.0",
"version": "1.0.1",
"keywords": "calibration, internal reference voltage, MCU clock, OSCCAL",
"description": "Supports calibration of OSCCAL and internal reference voltage and supoorts setting them at startup",
"repository":
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2 changes: 1 addition & 1 deletion library.properties
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name=avrCalibrate
version=1.0.0
version=1.0.1
author=Bernhard Nebel <nebel@hinterm-ziel.de>
maintainer=Bernhard Nebel <nebel@hinterm-ziel.de>
sentence=Determines calibration values for MCU clock frequency and internal reference voltage and sets them at setup.
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2 changes: 1 addition & 1 deletion readme.md
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Expand Up @@ -16,7 +16,7 @@ If you want to use only one of the values, then you still could use this functio

### Calibration process

The predetermined calibration values can either be stored in EEPROM or can be provided as constant values. The tricky part is, of course, to determine these calibration values. For that purpose, two Arduino sketches are provided in the `utility` folder. The `calibTarget` sketch needs to be loaded to the target board using a programmer. Before you do that, you need to adjust the compile-time constant `TRUEMILLIVOLT` to the true supply voltage of the target board (which should be measured using an accurate Multimeter). Next you need to upload the `calibServer` sketch to an Arduino UNO or similar board that uses a ceramic resonator or crystal. It generates a reasonably accurate 10 Hz signal that is used to calibrate the `OSCCAL` value on the target board.
The predetermined calibration values can either be stored in EEPROM or can be provided as constant values. The tricky part is, of course, to determine these calibration values. For that purpose, two Arduino sketches are provided in the `extras` folder. The `calibTarget` sketch needs to be loaded to the target board using a programmer. Before you do that, you need to adjust the compile-time constant `TRUEMILLIVOLT` to the true supply voltage of the target board (which should be measured using an accurate Multimeter). Next you need to upload the `calibServer` sketch to an Arduino UNO or similar board that uses a ceramic resonator or crystal. It generates a reasonably accurate 10 Hz signal that is used to calibrate the `OSCCAL` value on the target board.

You then need to connect the two boards using an ICSP cable (see below). Now open the monitor window and set the baud rate to 115200. After pressing the `RESET` button on the server board, which will also reset the target board, the calibration can be started by pressing a key. This could look like as in the following picture.

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