The Raspberry Pi has three types of serial interface on the GPIO header. You're probably already familiar with the UART serial port, which allows you to open a login session from a serial terminal application, such as PuTTY. The other two serial interfaces are the Serial Peripheral Interface (SPI) and Inter-Integrated-Circuit bus (I2C). Read an LDR On The Raspberry Pi Using An MCP3008. The Microchip MCP3008 ADC is a 10-bit Analog to Digital (A/D) converter with on-board sample and hold circuitry. Communication with the device is accomplished using a simple serial interface compatible with the SPI protocol.

The Pi Wedge helps access the I2C and SPI signals.This tutorial will walk you through getting the I2C and SPI interfaces of your Raspberry Pi working. These interfaces aren't enabled by default, and need some extra configuration before you can use them. Recommended ReadingBefore we get started, you might want to review some related background material. is a useful bus that allows data exchange between microcontrollers and peripherals with a minimum of wiring. is a cousin of I2C with similar applications. For the C/C examples, we'll be using the library to interface with these buses.

For the examples, we'll be using for SPI and smbus for I2C. Background & Software SetupThe Raspberry Pi has three types of serial interface on the GPIO header.

You're probably already familiar with the UART serial port, which allows you to open a login session from a, such as.The other two serial interfaces are the Serial Peripheral Interface ( SPI) and Inter-Integrated-Circuit bus ( I2C). On the Pi allows for up to two attached devices, while potentially allows for many devices, as long as their addresses don't conflict. Software DetailsThe software landscape for the Raspberry Pi has evolved considerably since the introduction of the Pi. Many different operating systems have been ported to the Pi, and the device driver infrastructure has also changed quite a bit.For this tutorial, we'll be using a recent version of Raspbian (installed via NOOBS), and the wiringPi I/O library for C/C (or spidev/smbus for Python).With the implementation of device tree overlays in Raspbian, some of the specific interface enablement details have changed.

If you're working with an older install, it might be worth backing up your SD card, and starting with a fresh install. OS and Library InstallIf you're starting from scratch, with a blank SD card, you'll want to install Raspbian. If you've already got a working Raspbian system, skip ahead to step 3. Download the image. As of this writing, it's at version 2.8.2. Follow the official.If you would like alternative ways to set up your Pi, please refer to the following tutorials. C/C (Wiring Pi) SetupIf you're planning on using C/C, Follow the to get git, update and upgrade your Rasbpian packages, then install WiringPi.Be patient - each of these steps takes a while.Once you've got wiringPi installed, run the gpio commands shown below.

Language:bashgpio -vgpio readallIt should respond with some information about the wiringPi version and the Pi that its running on, then draw a table illustrating the configuration for the pins in the 40-pin connector.The I2C and SPI interfaces each require some additional configuration and initialization, which we'll cover in later sections. Python (spidev/smbus) SetupFollow the to set up Python 3 and install pip. Raspi-config for SPIThe system will reboot. When it comes back up, log in and enter the following command language:bashls /dev/.spi.The Pi should respond with language:bash/dev/spidev0.0 /dev/spidev0.1These represent SPI devices on chip enable pins 0 and 1, respectively.

These pins are hardwired within the Pi. Ordinarily, this means the interface supports at most two peripherals, but there are cases where multiple devices can be daisy-chained, sharing a single chip enable signal. Programming Example Required Materials. The. A or single board computer.

A. Some. Headers of your choice. A display.The Serial 7-Segment display is particularly useful for testing serial interfaces, because it can accept command from a UART, SPI, or I2C.

Doctor who magazine 536 cbr. Make sure to header pins on the 7-segment display before wiring. Hookup TableThe display was connected to the Pi, via the Pi Wedge, as follows. Raspberry Pi SignalSerial 7-seg SignalGNDGND3.3VVCCCE1SS (Shift Select)SCKSCKMOSISDIMISOSDOThe test hardware looked like this.

Raspi-config for I2CThe system will reboot. When it comes back up, log in and enter the following command language:bashls /dev/.i2c.The Pi should respond with language:bash/dev/i2c-1Which represents the user-mode I2C interface. UtilitiesThere is a set of command-line utility programs that can help get an I2C interface working. You can get them with the apt package manager. Language:bashsudo apt-get install -y i2c-toolsIn particular, the i2cdetect program will probe all the addresses on a bus, and report whether any devices are present. Language:bashpi@raspberrypi:/$ i2cdetect -y 10 1 2 3 4 5 6 7 8 9 a b c d e f00: -10: -20: -30: -40: -50: -60: 60 -70: -This map indicates that there is a peripheral at address 0x60. We can try to read and write its registers using the i2cget, i2cset and i2cdump commands.

Programming Example Required Materials. The.

A or single board computer. A. Some. Peachtree quantum download. Header pins of your choice.

An digital-to-analog converter.Hookup TableThe display was connected to the Pi, via the Pi Wedge, as follows. Raspberry Pi SignalMCP4725GNDGND3.3VVCCSCLSCLSDASDAThe test hardware looked like this. I2C-0 on 40-pin Pi Boards An Extra I2C bus?As part of the B+ improvemets, the Raspberry Pi Foundation has standardized the interface to add-on boards, in what they call the specification.

It standardizes the physical form factor for add-on boards, and includes a provision for the B+ to automatically identify and initialize HATs at startup. It uses an I2C bus to read a description from an EEPROM on the HAT, similar to on the Beagle Bone Black.This capability has been carried forward on the A+ and Pi 2 Model B as well. This I2C bus is found on the IDSC and IDSD pins (pins 27 and 28 of the 40-pin connector) - but before you get too excited about adding peripherals on that bus, observe the note in the schematic for that port. Schematic snippet for 40-Pin GPIO connector (J8). Click on the image for a closer look.This is further clarified in theOn a Model B+, GPIO0 (IDSD) and GPIO1 (IDSC) will be switched to ALT0 (I2C-0) mode and probed for an EEPROM.

These pins will revert to inputs once the probe sequence has completed.The only allowed connections to the ID pins are an ID EEPROM plus 3.9K pull up resistors. Do not connect anything else to these pins!It's only there to talk to EEPROMs at addresses 0x50 during boot time. User access at runtime is problematic. If you want a general purpose I2C bus on the B+, you'll need to use I2C-1, on pins 3 and 5 of the 40-pin connector, marked SDA and SCL on the Pi Wedge. Enabling I2C-0I2C-0 is disabled by default. To enable it, you'll need to manually edit the configuration file.Edit /boot/config.txt, and add the following line. If you previously used raspi-config to enable I2C-1 and SPI, you'll see similar entries near the bottom of the vile.

Language:bashdtparam=i2cvc=onWith that enabled, restart your Pi ( sudo reboot). When it's back up, you'll know it's been activated if you've got a filesystem node at /dev/i2c-0. EEPROM Diagnostic ToolsAlongside the HAT design guide, there is a directory with some for working with HAT EEPROMs. To use them, download them and then make them from the command line.We'll explore how they're used below.

Testing I2C-0With the information above, we grabbed a EEPROM chip, and wired it to our Pi. We strapped all of the address pins to ground, which puts it at address 0x50, which we were able to confirm with i2cdetect. EEPROM on breadboardPull the EEPROM utilities mentioned above. The file testsettings.txt is a human-readable example of an EEPROM file. For testing purposes, we edited this file, changing the vendor and product fields to relevant information.The text file itself needs to be processed into a binary format before it can be written to the EEPROM. The eepmake utility handles this conversion. Language:bash./eepmake testsettings.txt test.eepWith the binary test.eep in hand, it can be programmed using the eepflash.sh script.

It takes a number of parameters, which are explained if you run it with the -h flag. When writing the EEPROM, you'll also have to approve of the operation by typing the full word yes when it prompts ( a simple y is not acceptable). Eepflash.sh will print out the status of the write - the 118 bytes written matches the length of the test.eep file we generated above. Language:bashsudo sh./eepflash.sh -w -f=test.eep -t=24c256This will disable the camera so you will need to REBOOT after this process completes.This will attempt to write to i2c address 0x50. Make sure there is an eeprom at this address.This script comes with ABSOLUTELY no warranty.

Continue only if you know what you are doing.Do you wish to continue? TroubleshootingIf you've gone through raspi-config and enabled the SPI/I2c from 'Advanced Options', yet the devices are not in the device tree, don't lose hope. There are two files that should be examined. We found that somtimes the raspi-config utility doesn't solve the problem, depending on what version of Pi, where raspbian was sourced from, and when the last update has occurred. Check /boot/config.txtSometimes the raspi-config tool will incorrectly edit /boot/config.txt while selecting the advanced settings. What happens is an erroneous control-char is placed in the file. Resources and Going FurtherFor digging deeper into the concepts covered in this tutorial, please see the following:.

If you're really curious about the nitty-gritty internal details of I2C and SPI, you might want to read the source code of Wiring Pi, which you can clone from. Additionally, you can learn about the Linux underpinnings of these interfaces documented at. The documentation seems to be more complete than its sibling. If the example code here isn't working, you should check for updated versions on the 40-pin Pi Wedge.

The way that I2C and SPI devices are enabled in Raspbian has changed significantly in recent revisions. Explains how to re-enable the interfaces if they disappeared in an upgrade. The HAT specifications and related information are hosted on.