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README.md

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