Alamode And Raspberry PI

Introduction

1. ATMEGA328P 8bit microcontroller
2. Precision real-time clock (RTC)
3. Micro SD card reader
4. Reset button
5. Standard shield headers

• Why Alamode?
• Setting up Alamode for Raspberry PI
• Behind the scene of Alamode
• Demo Code
• Common Problems
• Why Alamode?

1. Inbuilt high precision real-time clock with an integrated temperature-compensated crystal oscillator.
2. Supports built-in micro SD card reader. You can make use of it to read and write some useful information.
3. One can make use of the alamode analog pins and program with Arduino sensors.
4. Supports all Arduino Uno and standard compatible shields.
5. In build GPS support for the Fastrax UP501 module.
6. Interface with Raspberry PI via I2C, SPI or Serial UART.

Now it’s the time to set up an alamode package. Run the below mentioned command from your terminal. What we are trying to do is, connect to git repository and get the required setup files for alamode. There is a reason why we have to set up the alamode. Coming next you will understand. Once the above command runs successfully, you should be able to see the alamode-setup.tar file which we will have to extract using tar command. Navigate to the alamode setup folder and run the setup program. The setup runs within a second. You will have to restart Raspberry PI to see the changes. Behind the scene of Alamode Before we start discussing the scene of Alamode, there are various configuration changes that I am going to discuss. You don't really have to worry about these configurations as it's all taken care of by the Alamode setup program. As I have mentioned previously, the Alamode's heart is the same Arduino Uno microcontroller. We will see how the Alamode communicates with the Raspberry PI through serial UART. For those of you, who have some experience or understanding in connecting Raspberry PI to Arduino, you wouldn’t be much surprised in the way it works. Still, I am putting together some of the aspects that might help in understanding the way how the Alamode works with Raspberry Pi. We will not get into the details about the board schematics etc. but let us try to understand the high-level things which might be beneficial to you in understanding the reason behind setting up the alamode. Or say you want to know how the Raspberry PI and alamode communicate with each other, you will have to understand the basics about UART (Universal Asynchronous Reception and Transmission). Feel free to have a look into the following link to have some understanding of UART. Note: The alamode supports I2C, SPI or Serial UART when you are interfacing with Raspberry Pi. But it makes use of Raspberry PI’s Serial UART for uploading sketches. Before we dig into the details, let us see how the Raspberry PI supports communication with the external device. Here’s the typical interfacing mechanism that you see in connecting two devices and communicate with each other by sending and transmitting data to and fro using TX and RX connections. The serial interface in Raspberry PI consists of two signals the TX and RX which are used for transmitting and receiving bits. In order to communicate with an external device with serial communication over UART, you will have to connect the TX of Raspberry PI to the RX of the connected device and similarly, the RX of the PI has to be connected to the TX of the connected device such as Arduino. Note: The TX and RX are a part of the GPIO pins in Raspberry PI. It might look very simple, but there is something which we have to understand that is, the Raspberry PI runs with a voltage level of 0 and 3.3V logic levels whereas the Arduino runs with a voltage level of 0 to 5 volts. There is a voltage difference between these two devices and you wouldn’t be able to directly connect the TX and RX of each of these devices. You need an additional circuitry that is the voltage divider or a logical level convertor. However, when you are dealing with I2C communication with Raspberry PI as a master and the connected device such as Arduino as a slave, you don’t need a voltage divider. Let us now see how the alamode makes use of Raspberry PI’s serial UART for communication. Note - The Raspberry PI uses the UART as serial console input/output. We will have to disable in using a console and also in addition to that the Getty, a program that displays login screen has to be disabled too. You don’t really have to do any of these when you are using alamode for Raspberry PI. The reason being, when you are running the Alamode setup, it does everything for you. Edit the /etc/inittab file to disable gitty. You can do that by running the following command. In order to disable gitty, comment on the following line with a ‘#’ sign in front of it. When the Raspberry Pi boots up, by default it sends data over the serial port. Now we have to disable the same from using console so that the alamode can use it for communicating with the Raspberry Pi. For that, you have to remove the following information from /boot/cmdline.txt. Finally, you will have to reboot the Raspberry Pi. We have now understood the communication between Raspberry Pi and Alamode. There is more to know. When you are running the Alamode setup, if you open up the setup file you will notice below lines which do exactly the same I mentioned above for disabling the serial console for ttyAMA0 from boot -> cmdline.txt and also removes an entry in etc/inittabbk. The following things are part of the Alamode setup. When you are running the setup, it copies the “avrdude” and the associated configuration file “avrdude.conf” to the required directories. You will see next, the reason why we have to copy these files. The boards.txt is the file that avrdude program looks into forgetting the board information for uploading the HEX code. The avrdude makes use of the upload.speed as a baud rate for uploading code. Here’s the snippet of the Alamode board info. Creating dev rules for Alamode so that we are naming the devices. The setup has the following information for copying the dev rules and setting up the permissions for avrdude so that when you are uploading Arduino sketches, behind the scene it uses the avrdude. You definitely have to set up permission to run the avrdude. Within the Alamode, you will notice the avrdude and avrdude.conf. These are nothing but the modified version of the actual program used for uploading code from Arduino. Ideally, the Arduino IDE has no knowledge about the Alamode. If you open up the avrdude.conf, has the programmer for Alamode which will be used by avrdude while you are uploading the sketches. Running the setup program for Alamode overwrites the files so that when you open up the Arduino IDE, you will be able to select the board, programmer and since we are enabling serial port, you should also be able to select the serial port for uploading code. Demo Code

Let us now walk through with an example to understand how you can use Alamode with Raspberry PI. We will be using the simple blink sketch which comes with the Arduino samples. Open up Arduino IDE in Raspberry PI and use the following code for testing your alamode to see how it works by blinking an LED on PIN 13 with a one-second delay. Then select the serial port and “dev/ttyS0”. Compile or upload the sketch which will compile and upload the HEX code for our blink sketch to Alamode. You should be able to see the LED blinking at PIN 13. Note: There is a small LED onboard in Alamode on D13, which should start glowing with a 1s delay.

1. One common problem which you might encounter while uploading the sketch is:
   avrdude: ser_recv(): programmer is not responding.
   avrdude: stk500_recv(): programmer is not responding.
   This happens for various reasons. If you wish to know more information about the problem, under Arduino preferences, you can set the show verbose output during upload so that should give more information about the problem. I had encountered a similar issue, the microcontroller was unable to respond during the upload and there wasn’t an issue with the Alamode but I later realized the fact that the GPIO pins of Alamode were not rightly in place with the Raspberry Pi. There was a slight gap and I happened to slant the Alamode a bit so that the Raspberry PI’s GPIO is fully in contact with the Alamode.
2. There are cases where the serial port is in use, in such cases, you won’t be uploading the sketch. Make sure the serial port /dev/ttyS0 is not in use while you are uploading the sketch.
3. There are times you are unable to select the serial port from Arduino IDE.

Note: This should not happen if you have installed the Alamode correctly. But if it happens don’t worry; you can manually update the boot/cmdline.txt and /etc/inittab as I have explained earlier.