Spiff's Electronics Notebook

Fading LED default test sketch (February 12, 2009)

For some time now, every Arduino bootloaded ATmega we've shipped has come with a default testing sketch that slowly pulses the LED on and off in a cyclic fashion.

A "fading" sketch using hardware PWM is included in the IDE distribution under Examples→Analog→Fading to fade an LED, but the Pin 13 status LED isn't connected to a hardware PWM pin.

The answer is to abuse the delayMicroseconds call to create crude software PWM. By setting the pin high; delaying; setting the pin off; and delaying for a different period, we can change the brightness simply by altering the delay.

One catch to this approach, is if you use purely the on/off delay to control the PWM speed, you're left with either a very fast fade or an unsettling flashing. Instead we keep the delay between 4 and 250 µs (about 3 to 4kHz) and add an additional loop around each on/off loop to set the fading speed. --You can't set the delayMicroseconds code to 0 or you'll get an unexpectedly long delay.

Finally, we use the serial port to output a rising count, just to ensure the serial port works.

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Arduino Atmel Code Freeduino Kit
Posted by spiffed at 11:11 AM

Arduino and Freescale MPX Pressure sensors (April 29, 2008)

Freescale makes a range of integrated pressure sensors with 0-5V analog outputs, in a vast array of configurations. Today, I've picked the MPXV5010DP, but you should be able to adapt this to a range of sensors.

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Arduino Atmel Code Freeduino Howto Pressure Sensor
Posted by spiffed at 12:10 AM | Comments (0)

EEPROM read/write code for CC5X (January 30, 2008)

CC5X may already include internal-EEPROM handling code, but I couldn't find any. With this in mind, here are two short methods for writing and reading from the EEPROM in many PIC microcontrollers. (Based on Microchips datasheets and .)

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CC5X Code EEPROM Howto PIC
Posted by spiffed at 12:00 AM | Comments (0)

Getting up to speed with the PIC16F737 (January 29, 2008)

Porting code between PIC micros from the same product range is normally a smooth process: redefine a few pins, change some clock-speed constants, and add support code for that new integrated peripheral widget.

Sometimes though, there's a large hurdle before you can even begin. The 16F737 posed such a hurdle, there are a few clever lines of code required to put the device into all digital I/O running under the internal oscillator (intosc).

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Code PIC
Posted by spiffed at 10:44 PM | Comments (0)

Serial LCD Controller (June 26, 2005)

makes a number of rather nice serial (and USB based) LCD and VFDs. What they do not make, are inexpensive LCDs. Thankfully, hacking serial onto a cheap parallel LCD is sometimes almost as good.

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Code Kit LCD PIC Serial SerialLCD
Posted by spiffed at 1:11 PM

Digital Input to the PIC16F628 in C (March 26, 2005)

I recently mentioned that I could not convince C to read from PORTA of a PIC. I have seen the error of my ways. The only thing missing from my code was a single line to disable analog functions on PORTA. inserting CMCON = 0x07; into the top of main() nicely fixed the mysterious I/O failures.

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Code Howto PIC
Posted by spiffed at 12:46 PM

Blinkin' PIC (March 24, 2005)

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Code Howto PIC
Posted by spiffed at 9:23 PM