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Step 9Building the Main Circuit
In this step we'll prototype the heart of the circuit. You'll need your microcontroller, the 4MHz crystal, two 22pf ceramic capacitors, a 10k resistor and some wires for VCC and ground. We'll also put in a couple of LEDs so that we can run a test app to make sure everything works.
Place the microcontroller on the breadboard so it straddles the middle trench. This way, again, we don't connect opposite pins to each other.
First, pin 1. This is reset and should be held at logical 1 for the chip to work. Connect it to the +5V voltage rail by means of the 10k resistor (and some wire if you need it).
Working down, we get to pins 7 and 8. These are VCC and ground respectively. Connect up pin 7 with a (red) wire to the 5V rail and pin 8 to ground.
On the opposite side, connect pin 20 up to VCC too (AVCC) and ground pin 22.
Place the crystal so it connects up pins 9 and 10. Then, connect a capacitor from each of these pins to ground (you can just put the capacitors so they feed into the ground pin).
For the LEDs we're going to use pins 24 and 25. Put a resistor and LED in series with each pin (going to ground). Check the LED polarity is correct (it's unlikely you'll actually burn it out with the low voltages if you wire it backwards, but it won't turn on). The negative leg is on the same side as the flat indent in the plastic casing.
Check the pictures below to compare with your circuit and continue!
Place the microcontroller on the breadboard so it straddles the middle trench. This way, again, we don't connect opposite pins to each other.
First, pin 1. This is reset and should be held at logical 1 for the chip to work. Connect it to the +5V voltage rail by means of the 10k resistor (and some wire if you need it).
Working down, we get to pins 7 and 8. These are VCC and ground respectively. Connect up pin 7 with a (red) wire to the 5V rail and pin 8 to ground.
On the opposite side, connect pin 20 up to VCC too (AVCC) and ground pin 22.
Place the crystal so it connects up pins 9 and 10. Then, connect a capacitor from each of these pins to ground (you can just put the capacitors so they feed into the ground pin).
For the LEDs we're going to use pins 24 and 25. Put a resistor and LED in series with each pin (going to ground). Check the LED polarity is correct (it's unlikely you'll actually burn it out with the low voltages if you wire it backwards, but it won't turn on). The negative leg is on the same side as the flat indent in the plastic casing.
Check the pictures below to compare with your circuit and continue!
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