102 lines
2.6 KiB
Markdown
102 lines
2.6 KiB
Markdown
# AVR ATiny13 Project 002
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This is the firmware for a latching dual relay system. It allows the user to
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switch two DPDT relays by with two separate switches.
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## Components:
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**Micro:** AVR ATiny13, ATiny25/45/85
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## Instructions:
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1. Power the system using a 1.8v~5.5v power supply
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2. Set/program the AVR to use a 1MHz clock rate.
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3. Connect the pins as described above.
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**ACTIVATING RELAYS:**
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1. Activate the desired button with a quick press <= 350ms.
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2. Repeat to toggle the relay.
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**TEMPORARY TOGGLE:**
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1. Press and hold the desired button >= 350ms.
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2. Let go to disable.
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**SAVING SETTINGS:**
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1. Press and hold the target button.
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2. While holding the button power cycle the device.
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3. When the setting is successfully saved the relay/led will blink/toggle.
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4. repeat until desired preset is saved.
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## Technical Aspects:
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The use of C style bitfields has been used inside a struct to maintain a global
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state. It minimizes the size of the binary once compiled.
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The majority of the code is blocking/polling; overhead from introducing
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interrupts and ISR(interrupt service routines) wasn't as clean and made it more
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platform dependent.
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The code right now can for the most part be ported to any AVR micro-controller
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with no changes.
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## Timings
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The current setup is calculated for a attiny13/a running at 4.8Mhz without the
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clock divider fuse set.
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This means that the actual f_cpu is 4.8Mhz to calculate the delay times
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we can use this formula:
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$$
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msPerOverflow = 1000ms / (\frac{4.8Mhz}{64} / 256) \approx 6.8ms
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$$
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Where $64$ is the pre scaler setting and $256$ is the maximum value of the 8bit
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timer.
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## BUILDING PROJECT:
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**On Unix**
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```sh
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git clone <REPOURL>
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cd <REPO>
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make flash
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```
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## Flashing the Project
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**On Windows(usbtinyisp)**
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1. Install the usbtiny driver:
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1. plug in usbtiny device
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2. Install the drivers from: [adafruit](https://learn.adafruit.com/usbtinyisp/drivers)
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2. open Powershell
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3. navigate to the repo directory *cd Downloads\gf_002*
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4. enter the command below.
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```ps1
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./avrdude.exe -p t13 -c usbtiny -B 125kHz -U flash:w:.\pre_built\attiny13_4-8Mhz.hex -U lfuse:w:0x79:m -U hfuse:w:0xFF:m -U lock:w:0xFF:m
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```
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**On Windows(usbASP)**
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1. Install the usbasp driver:
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1. plug in usbasp device
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2. run the 'zadig-2.8.exe' program
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3. select the libusb 32 on the right by clicking the down arrow to select.
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2. open Powershell
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3. navigate to the repo directory *cd Downloads\gf_002*
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4. enter the command below.
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```ps1
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./avrdude.exe -p t13 -c usbasp -B 125kHz -U flash:w:.\pre_built\attiny13_4-8Mhz.hex -U lfuse:w:0x79:m -U hfuse:w:0xFF:m -U lock:w:0xFF:m
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```
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