Draw patterns on the 8 × 8 matrix

Keep U S B disconnected while you build. On this breadboard, each group of five holes shares a connection; the centre channel separates the two halves. You can drag the 3D view to look around. Start with the supply. Connect the Arduino’s five volt output to the positive rail. That rail will power the display driver. Now connect Arduino ground to the ground rail. The driver and Arduino need this shared reference. The MAX7219 handles the fast scanning for us. Seat it across the centre channel, with its pin-one notch at the left. Add the mini breadboard beside the main board. The matrix will bridge the gap, leaving its connections accessible on both sides. This build uses the row-anode, column-cathode pin map listed below. Check your matrix against that map first, then seat it in the highlighted holes. Its display face stays clear of the wiring. Add the one hundred kilohm resistor here. It sets a low starting L E D current through the driver’s ISET pin. A resistor works in either direction. This one hundred nanofarad capacitor helps keep the driver’s supply steady during switching. It spans the positive and ground rails and has no polarity. The ten microfarad capacitor adds a little more supply buffering. Its positive lead goes to the positive rail; the stripe marks the negative lead, which goes to ground. Connect the driver’s power pin to the positive rail. This is its five volt supply. Connect the first ground pin on the driver to the ground rail. There’s a second ground pin on this driver. Connect that to the same ground rail too. Connect ISET to one end of the current-setting resistor. This is how the driver sets the L E D current. Connect the other end of that resistor to the positive rail. Connect digital pin eleven to the driver’s data input. This is the Uno’s controller data output pin; our program uses S P I to send the pattern data. Connect digital pin thirteen to the clock input. This is the S P I clock, which tells the driver when to read each bit. Digital pin ten connects to LOAD. The program pulses it to finish each command. That completes the three control signals. Now connect the driver’s segment D P output to the first anode row of the matrix. These segment outputs supply the rows, while the digit outputs will select the columns. Connect segment A on the driver to row 2 of the matrix. Connect segment B on the driver to row 3 of the matrix. Connect segment C on the driver to row 4 of the matrix. Connect segment D on the driver to row 5 of the matrix. Connect segment E on the driver to row 6 of the matrix. Connect segment F on the driver to row 7 of the matrix. Connect segment G to the eighth anode row. That finishes the row connections; next are the column returns. Connect digit zero on the driver to the first cathode column. These are switched returns, not ground wires: the driver selects each column in turn. Connect digit 1 on the driver to column 2 of the matrix. Connect digit 2 on the driver to column 3 of the matrix. Connect digit 3 on the driver to column 4 of the matrix. Connect digit 4 on the driver to column 5 of the matrix. Connect digit 5 on the driver to column 6 of the matrix. Connect digit 6 on the driver to column 7 of the matrix. Connect digit seven to the eighth column. With all the rows and columns connected, the driver can scan the whole matrix. Check all wiring. Connect the square U S B-B plug to the Uno and the U S B-A plug to your computer. Use Verify and Upload in the code editor below.

Keep U S B disconnected while you build. On this breadboard, each group of five holes shares a connection; the centre channel separates the two halves. You can drag the 3D view to look around.

Start with the supply. Connect the Arduino’s five volt output to the positive rail. That rail will power the display driver.

Now connect Arduino ground to the ground rail. The driver and Arduino need this shared reference.

The MAX7219 handles the fast scanning for us. Seat it across the centre channel, with its pin-one notch at the left.

Add the mini breadboard beside the main board. The matrix will bridge the gap, leaving its connections accessible on both sides.

This build uses the row-anode, column-cathode pin map listed below. Check your matrix against that map first, then seat it in the highlighted holes. Its display face stays clear of the wiring.

Add the one hundred kilohm resistor here. It sets a low starting L E D current through the driver’s ISET pin. A resistor works in either direction.

This one hundred nanofarad capacitor helps keep the driver’s supply steady during switching. It spans the positive and ground rails and has no polarity.

The ten microfarad capacitor adds a little more supply buffering. Its positive lead goes to the positive rail; the stripe marks the negative lead, which goes to ground.

Connect the driver’s power pin to the positive rail. This is its five volt supply.

Connect the first ground pin on the driver to the ground rail.

There’s a second ground pin on this driver. Connect that to the same ground rail too.

Connect ISET to one end of the current-setting resistor. This is how the driver sets the L E D current.

Connect the other end of that resistor to the positive rail.

Connect digital pin eleven to the driver’s data input. This is the Uno’s controller data output pin; our program uses S P I to send the pattern data.

Connect digital pin thirteen to the clock input. This is the S P I clock, which tells the driver when to read each bit.

Digital pin ten connects to LOAD. The program pulses it to finish each command. That completes the three control signals.

Now connect the driver’s segment D P output to the first anode row of the matrix. These segment outputs supply the rows, while the digit outputs will select the columns.

Connect segment A on the driver to row 2 of the matrix.

Connect segment B on the driver to row 3 of the matrix.

Connect segment C on the driver to row 4 of the matrix.

Connect segment D on the driver to row 5 of the matrix.

Connect segment E on the driver to row 6 of the matrix.

Connect segment F on the driver to row 7 of the matrix.

Connect segment G to the eighth anode row. That finishes the row connections; next are the column returns.

Connect digit zero on the driver to the first cathode column. These are switched returns, not ground wires: the driver selects each column in turn.

Connect digit 1 on the driver to column 2 of the matrix.

Connect digit 2 on the driver to column 3 of the matrix.

Connect digit 3 on the driver to column 4 of the matrix.

Connect digit 4 on the driver to column 5 of the matrix.

Connect digit 5 on the driver to column 6 of the matrix.

Connect digit 6 on the driver to column 7 of the matrix.

Connect digit seven to the eighth column. With all the rows and columns connected, the driver can scan the whole matrix.

Check all wiring. Connect the square U S B-B plug to the Uno and the U S B-A plug to your computer. Use Verify and Upload in the code editor below.