Half of the reason I want to use the ETH is because it is “historical” in it being retired (and I can still get my hand on) and that is what the Arduino IDE see the Arduboy as. But that is the same price as a manufactured Arduboy so I kind of not want to do it.
I am just curious about the PINs, as the chart above (somewhere) list them in one column.
I am GOING to create a Arduboy clone. I am currently considering NOT a micro or a micro pro. Boards listed by you are awesome choices as no changes need to be done. I am thinking maybe a Esplora, a Mega2560, Leonardo or Leonardo ETH.
Esplora was too unflexible, and buying a already-made gameboy costing more without a case and a screen is not what I am going to do.
The main reason for getting a Leonardo ETH would be if you want to use the ethernet part of it. I had a quick glimpse at thje schematic and noticed something that makes it not suitable for a selfmade Arduboy:
pin PD4 which is used for OLED DC (OLED data/ command select) on Arduboy is used as SD card select on the Leonardo ETH.
The MEGA doesn’t use an ATMEGA32U4 as MCU so there may be software issues to deal with.
do you want to free-up pin 6 for another function or just want to ground your speaker?
in the last case you can just connect your speaker between pin 5 and ground.
However If you’re going to hook both your Arduboy clone and another device to the same speaker pin, you need to have some protection from the pins shorting each other (one device output low, other device high or vice versa will cause a short)
if you’re using a piezo speaker adding a 1K resistor at each device output would be fine. If you’re using an actual (low impedance) speaker you’d better drive the speaker pin using a transistor (each device drives a transistor, so you need two)
I want to ground one of the speaker pins to make it compatible with my other audio sources. My plan is to add an FM receiver and MP3 player in the same enclosure along with Arduboy. In future, I might also want to add some sensors or want to control any other gadget from the same MCU, hence freeing up a pin or two will be convenient.
I am not sure how the current audio implementation of Arduboy works with 2 pins; At first, I assumed one pin is used for generating tones and the other pin is used for controlling volume level. Or there may be a complex audio generation by using both pins as different frequency generator.
I have just started learning MCU and embedded C, and mostly learning by practical experimentation. Understanding the code base is difficult and time consuming for me as I have to grab many new concepts on the fly. Wish there were some content describing the Arduboy codebase and hardware.
After reading reply from you and @MLXXXp, I am thinking of trying a single transistor adder ckt as below:
In 1 ------\/\/\/------|. . . . . . |/--------- + Vcc
In 2 ------\/\/\/------|----------|
In 3 ------\/\/\/------|. . . . . . |\>------- Out/Spk +
In the Arduboy, one pin is connected to one of the speaker leads. The second pin is connected to the other speaker lead, rather than grounding this speaker lead.
Since each pin can sink as well as source current, you can leave one pin low (or high) and it will provide a return path for a signal generated on the other pin. (Therefore, note that in order to hear sound generated from one pin, the other pin must be set as an output.)
As a side note: The piezo speaker used is essentially a capacitor, so you can’t damage anything by having one pin permanently high and the other permanently low. It will just “charge” the speaker/capacitor. (If you were to use a low impedance “voice coil” type speaker with this arrangement, you would need a suitable capacitor in series with the speaker to block any DC component of the signal.)
Now, if an audio signal is put on one pin and another audio signal, with the phase reversed, is put on on the other pin, it ends up mixing the two signals. This allows a single speaker to play two distinct audio signals, the same as if the signals had been mixed by some other method. The ArduboyPlaytune library uses this to allow playing a two part score with each part on a pin, or a single part score on one pin while outputting tones on the other pin.
Another thing the circuit is capable of: If you place identical signals on each pin but with one having a reversed phase to the other, you will get a higher volume than if one pin was held constant. (The voltage on the speaker will be doubled.) The ArduboyTones library uses this technique to allow any tone to be played at either “normal” or “louder” volume.
As I described in my post above, if you plan on mixing the two pins from an Arduboy compatible, the signal from one of the pins should be inverted (phase reversed), and possibly capacitively or AC coupled, which is what attaching the two pins directly to a piezo speaker does.
This topic is initially about @Mr.Blinky reporting that Aruduino Pin 6 can be used to replace Pin 13 (used by the Arduboy along with Pin 5 for the speaker) to output the compliment of Pin 5, for higher volume. The reason for using Pin 6 is that Pin 13 isn’t available on the Sparkfun Pro Micro board, which many people use for making Arduboy “clones”.
Pin 6 doesn’t provide anything that can’t be done with Pin 13 on a real Arduboy.
You get a louder volume by driving one speaker pin high whenever the other pin is low, as compared to just leaving one pin fixed low or high. It doubles the voltage of the waveform presented to the speaker. As I stated earlier in this thread:
ATMlib and ArdVoice also use it permanently because the PWM generated waveforms they produce tend to be lower average volume than what you get from simple square wave tones.
Yes. For full compatibility, you need both pins and one should be inverted.
Sometimes only one pin is used.
Sometimes only the other pin is used.
Sometimes both pins are used with different sounds on each.
Sometimes both pins are used with one being the compliment of the other for higher volume.
Also, using the transistor as a simple saturated switch for PWM digital signals, with full swing, might be okay but if any of your sources are true analogue signals you’ll probably need to bias the transistor as a true amplifier or use some other analogue amplifier circuit.
As for the capacitor and resistor values, you may have to experiment to determine what’s best.