Category: Raspberry Pi

Sometimes you just want to connect your Raspberry Pi to your Wifi immediately when you first install RetroPie or Rasbian just so you can tinker with it soon and setup some stuff.

STEP 1. On a Windows PC insert your newly installed SDCard

With the sdcard plugged in (USB SDCard reader) your Windows 10 computer, fire up File Explorer and go to the boot partition of your sdcard.

Step 2. Setup Network or WiFi Info

Create a file called wpa_supplicant.conf inside the boot partition of the sdcard. Open it with any text editor like notepad and paste the following.

country=US
ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
    ssid="WIFI-NAME"
    psk="WIFI-PASSWORD"
}

Replace “WIFI-NAME” and “WIFI-PASSWORD” with your wifi details. Save and exit.

Step 3. Enable SSH

Enable SSH so you can connect to your raspberry pi from any computer. Create a blank file called ssh inside the same boot directory of your sdcard.

Finally, eject the sdcard properly and plug it in to your Raspberry Pi. Turn on your Pi and it should connect to your network automatically.

These are the pins for the left and right audio as well as composite video on any Raspberry Pi 3 models.

In order to avoid power related issues with any of the Raspberry Pi 3 model, it is recommended to just directly power it from your power supply (PowerBoost 1000c, GearBest PowerBoost, etc.).

So here’s how you would power your Pi 3 which is the same for all the models (Model B, Model B+, Model A+). The PP2 pad goes to the 5V+ output of your Power Supply and the PP5 pad goes to the GND output of your Power Supply. Use a wire that’s 24-26awg in size.

I’m always looking for ways to save time so here’s how you can setup putty to automatically login to your Raspberry Pi.

Let’s Get Started

1. Go to the folder where you installed putty.exe, left click on it to select it, right click on it and choose “Create shortcut”. 
2. Select the newly created shortcut file, right click on it and select “Properties”. In the “Target” text field, add the line  pi@ip -pw raspberry replacing the ip with your Raspberry Pi’s ip address. 
3. Click OK and you’re done. Now every time you open the shortcut link it will automatically login to your raspberry pi.

That’s it! 🙂

This guide might also work on any screen that we use for building our Game Boy Zero as long it uses the CL6201 LED driver IC with the “7001” label on it.

I will be using a Raspberry Pi Zero for this tutorial but any Arduino/Atmel chips with PWM pins can also be programmed to do the job. I have actually tested it with an attiny13a and it works just fine.

Hardware

Before we start, follow the Wiring Guide for the 3.5″ GearBest Screen with 5V Mod. Then start by soldering a wire from the CL6201’s EN pin 4 to the Pi Zero’s GPIO19 pin. The CL6201 Datasheet says that the EN pin can be used to adjust the brightness by connecting it with a PWM square wave signal between 100Hz and 100KHz. That means with the Raspberry Pi’s capability to produce PWM signal we can control the brightness with it.

For the control buttons let’s use two tactile buttons for increasing and decreasing the brightness. Wire the buttons like this:

Software

You can write a program in Python or C to do the PWM routine but let’s keep it simple by using a progam called pigpio and write a simple python to just call it. Login to your Raspberry Pi and install the program by following the instruction at abyz.me.uk/rpi/pigpio/download.html.

Testing

We are now ready to test the program. Type the command sudo pigpiod to load the pigpio daemon. Now we can test it with the following command format:

pigs p GPIO DUTYCYCLE(0-255)

GPIO is the gpio pin we want to use which is GPIO19 and DUTYCYCLE is what controls the brightness.

Example:

pigs p 19 50

The above code should dim the screen. Try experimenting with other DUTYCYCLE values from 0-255.

Now for the actual buttons to control the brightness I wrote a simple python to call the pigpio program. Copy the code below and paste to a new file with .py extension. You can just name it as brightness_controller.py if you want.

import RPi.GPIO as GPIO

import subprocess
import time

dutycycle = 255
GPIO.setmode(GPIO.BCM)
BTTN_DIM = 15
BTTN_BRIGHT = 16
PWM_PIN = 19
 
GPIO.setwarnings(False) 

GPIO.setup(BTTN_DIM, GPIO.IN, pull_up_down=GPIO.PUD_UP)
GPIO.setup(BTTN_BRIGHT, GPIO.IN, pull_up_down=GPIO.PUD_UP)
cmd = "pigs p 19 " + str(dutycycle)
subprocess.call(cmd, shell=True)

def btn_func(a):
   global dutycycle
   global cmd
	
   if a == 1:
      dutycycle = dutycycle + 25
   else:
      dutycycle = dutycycle - 25
   
   cmd = "pigs p 19 " + str(dutycycle)   
   subprocess.call(cmd, shell=True)
    

GPIO.add_event_detect(BTTN_DIM, GPIO.FALLING, callback=lambda x: btn_func(0), bouncetime=300)
GPIO.add_event_detect(BTTN_BRIGHT, GPIO.FALLING, callback=lambda x: btn_func(1), bouncetime=300)

while 1:
   time.sleep(10)

Run it by typing the command  python brightness_controller.py. Press each of the buttons and it should increase or decrease the brightness on the screen.

Here’s a demo:

That’s it! Let me know in the comment below if this works for you.

The diagram below shows where to connect to the PWM audio on a Pi Zero(bottom view):

PWM0 and PWM1 are the right and left audio channels corresponding to GPIO 18 and GPIO 13 on the Pi Zero.

Your /boot/config.txt should include the following line: dtoverlay=pwm-2chan,pin=18,func=2,pin2=13,func2=4

First, let’s choose which device to use. Enter the command cat /proc/asound/modules to list all available sound devices whether it’s a PWM audio or USB sound device.

The command you just entered should output something like:

0 snd_bcm2835 << this is the PWM audio I configured on GPIO18 & GPIO13.
1 snd_usb_audio << this is my USB sound device.

Enter the command sudo nano /etc/asound.conf and paste the following code:

# convert stereo to mono LEFT output

pcm.monocard{
  slave.pcm "hw:N"
  slave.channels 2
  type route
  ttable {
    # Copy both input channels to output channel 0 (Left).
    0.0 1
    1.0 1
    # Send nothing to output channel 1 (Right).
    0.1 0
    1.1 0
  }
}

pcm.!default monocard

Change the N on the line slave.pcm "hw:N" to  the number that corresponds to the audio device you want to use. I will be using my USB audio device so mine should read slave.pcm "hw:1".

The above code uses both left and right audio input to output to LEFT channel. If you want the output to the RIGHT then you can just edit the line 8 – 14 to:

# Copy both input channels to output channel 1 (Right).
0.1 1
1.1 1
# Send nothing to output channel 0 (Left).
0.0 0
1.0 0

Restart ALSA by sudo /etc/init.d/alsa-utils restart or you can reboot your Raspberry Pi using sudo reboot.

Edit the following file:

/etc/usbmount/usbmount.conf

and remove “sync” from MOUNTOPTIONS

.

This is how you adjust the volume via the terminal or command line:

amixer sset PCM,0 75%

If you’re wondering how to test the left and right audio channel of your Raspberry Pi whether using an external USB sound device or the builtin audio you’ve come to the right place.

Connect to your Raspberry Pi via SSH or open the Terminal application. The simplest way to test the sound is to use the speaker-test command. Enter the following to test sound from your default configured audio device.

speaker-test -c2 -twav -l7

You should hear an alternating sound coming from your left and right speakers.

If you’re using a USB sound device you first need to check its device id/number.

Enter:

cat /proc/asound/modules

Output:

0 snd_bcm2835
1 snd_usb_audio

Then use speaker-test -c2 -twav -l7 -D plughw:N,0 replacing N with the number before snd_usb_audio. Like this:

speaker-test -c2 -twav -l7 -D plughw:1,0

Output should the same as the picture above and alternating sound from left and right audio from your speakers.

Using omxplayer to test mp3 or wav sound file

omxplayer example.mp3

The above command will auto-detect or use any default configured audio device. Otherwise, if you want to test your USB Sound device enter the following command with 1 as the device number:

omxplayer example.mp3 -o alsa:hw:1,0