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Printed circuit board ‘Multiuse tiny1’ using ATmega8




Project overview

This small PCB, which I named Multiuse tiny1 was originally designed to convert NES/SNES controllers to USB. Since there is not a lot of space availabe inside an SNES controller, I designed the PCB to be as small as necessary. The PCB has improved since the beginning, thanks to the many other uses I found for this PCB.

Characteristics:

  • Small: width=27.5mm, height=17.7mm, thickness=3.4mm (withou regulator) or 5.3mm (with regulator)
  • Atmel AVR Atmega8 microcontroller on-board.
  • The following microcontroller signals are available via solder pads: PC5(ADC5/SCL), PC4(ADC4/SDA), PC3(ADC3), PC2(ADC2), PC1(ADC1), PC0(ADC0), PB5(SCK), PB4(MISO), PB3(MOSI), PB2(SS/OC1B), PB1(OC1A), PB0(ICP1), PD0(RXD), PD1(TXD), PD2(INT0). Please note that PD0(RXD) and PD1(TXD) are tied together.
  • Optional voltage regulator can supply a lower voltage to the MCU and/or external peripherals.
  • This circuit is perfect for the Firmware-Only USB Driver from Objective development. All necessary components are there (Atmega8, 12mhz crystal with capacitors, 68 ohms resistors and zener diodes).

Printed circuit board

Known projects which use this PCB:

Programming:
To program the microcontroller, programmer wires must be soldered directly on the board. Just follow the schematic. Some programming signals (unfortunately not all) are available on the back side of the board.

USB:
When USB is not used, it is not necessary to solder the zener diodes nor is it necessary to install resistor R1. The 68 ohms resistors R2 and R3 may be replaced by 0 ohm resistors if you need to use those ports. (That’s what I did for the SNES/NES Gamepad to Gamecube/Wii adapter project.

Regulator:
The PCB backside has a footprint for an lm1117 voltage regulator. 0 ohm resistors or solder bridges must be installed to select the power source for the microcontroller and the circuit output.

When no regulator is needed, installing U3, R9, R10, C5, R7 and R8 is not necessary. But dont forget to install R6, R6 and C1.

The voltage regulator has an adjustable output. Here is a convenient tool you can use to calculate the output voltage that would be obtained depending on the selected resistors.

 

For more detail: Printed circuit board ‘Multiuse tiny1’ using ATmega8

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