Resetting an Adafruit Trinket using an Arduino Uno

satb100Sometimes when you’re designing electronic circuit boards especially on a budget it’s easy to cut corners and only put the very bare essentials into the board. But the folks at Adafruit Industries make quality inexpensive products and they never cut corners. Case in point is there new ATtiny85 development boards the Adafruit Trinket and Adafruit Gemma. Other boards using the ATtiny85 require you to physically unplug and re-plug their boards every time you want to load a new sketch. On the other hand Adafruit included a reset button and they broke out the reset line on one of the breakout pins. For most people that’s probably not a big deal but for someone with a disability with myself, the inability to physically plug and unplug the board is a dealbreaker. Thanks to Adafruit including this reset breakout I was able to use another microcontroller namely an Arduino Uno to toggle the reset for me and allow me to use the board despite my disability. Here is a demo video I created for the weekly Adafruit Show-and-Tell.

Here is a code used on the Arduino Uno to toggle the pin 5 low for 1/10 of a second
//Sends reset signal from Arduino to
//Adafruit trinket by pulsing the reset line
//low for 1/10 of a second
int reset_pin = 5;
void setup() {
pinMode(reset_pin, OUTPUT);
digitalWrite(reset_pin, HIGH);
delay(100);
digitalWrite(reset_pin, LOW);
delay(100);
digitalWrite(reset_pin, HIGH);
}
void loop() {
}

Here is the code that you load onto the trinket so that it will blink a particular pattern. That verifies that you successfully uploaded.
//Modified trinket blink sketch
int led = 1; // blink pin 1 the built in red LED
void setup() {
pinMode(led, OUTPUT);
}
void Signal (char N,int T) {
for(int i=0;i

Here is the Adafruit Show-and-Tell from September 21, 2013 where I demonstrated this project.

2 thoughts on “Resetting an Adafruit Trinket using an Arduino Uno

  1. Thanks for the tip.

    My project is based on a trinket, accelerometer and a 5-way button and I want people to upload new programs to the device.

    Using this technique on the same board is actually a great way to insure end users don’t hold the reset button down for more than 10 seconds and fry the bootloader. (read fewer tech support calls and returns)

    I’m going to count when the middle button is held down x seconds and then send your reset code.

    Thanks again

    • Keep in mind I’m using two different Arduinos. A trinket and an Uno. The Uno resets the trinket. I’m not sure what would happen if you tried to get the trinket to reboot itself. That might be problematic.

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