MICA+Mote+Specifications.jpg' alt='Silicon Serial Number Spi' title='Silicon Serial Number Spi' />Arduino and the SPI bus. Learn how to use the SPI data bus with Arduino in chapter thirty four of a series originally titled Getting StartedMoving Forward with Arduino by John Boxall  A seemingly endless tutorial on the Arduino universe. The first chapter is here, the complete series is detailed here. Updated 1. This is the first of two chapters in which we are going to start investigating the SPI data bus, and how we can control devices using it with our Arduino systems. The SPI bus may seem to be a complex interface to master, however with some brief study of this explanation and practical examples you will soon become a bus master To do this we will learn the necessary theory, and then apply it by controlling a variety of devices. In this tutorial things will be kept as simple as possible. But first of all, what is it And some theorySPI is an acronym for Serial Peripheral Interface. It is a synchronous serial data bus data can travel in both directions at the same time, as opposed to for example the I2. C bus that cannot do so. To allow synchronous data transmission, the SPI bus uses four wires. They are called MOSI Master out, Slave in. This line carries data from our Arduino to the SPI controlled devices MISO Master in, Slave out. Document Number 00200497 Rev. H Page 2 of 90 S25FL116KS25FL132KS25FL164K Logic Block Diagram Performance Summary Maximum Read Rates VCC 2. V to 3. 6 V, 85 C. SST26WF040B040BA SST26WF080B080BA DS20005283Bpage 2 2014 Microchip Technology Inc. TO OUR VALUED CUSTOMERS It is our intention to provide our valued customers. Product Folder Order Now Technical Documents Tools Software Support Community An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty. Learn how to use the SPI data bus with your Arduino, which opens up all sorts of possibilities. PIC16F88X DS80000302Jpage 2 20072014 Microchip Technology Inc. TABLE 2 SILICON ISSUE SUMMARY PIC16F882 Module Feature Item Number Issue Summary. This line carries data from the SPI controlled devices back to the Arduino SS Slave select. This line tells the device on the bus we wish to communicate with it. Each SPI device needs a unique SS line back to the Arduino SCK Serial clock. Within these tutorials we consider the Arduino board to be the master and the SPI devices to be slaves. On our Arduino DuemilanoveUno and compatible boards the pins used are SS digital 1. You can use other digital pins, but 1. SPI pins MOSI digital 1. MISO digital 1. SCK digital 1. Arduino Mega users MISO is 5. MOSI is 5. 1, SCK is 5. SS is usually 5. 3. If you are using an Arduino Leonardo, the SPI pins are on the ICSP header pins. See here for more information. You can control one or more devices with the SPI bus. For example, for one device the wiring would be Data travels back and forth along the MOSI and MISO lines between our Arduino and the SPI device. This can only happen when the SS line is set to LOW. In other words, to communicate with a particular SPI device on the bus, we set the SS line to that device to LOW, then communicate with it, then set the line back to HIGH. If we have two or more SPI devices on the bus, the wiring would resemble the following Notice how there are two SS lines we need one for each SPI device on the bus. You can use any free digital output pin on your Arduino as an SS line. Just remember to have all SS lines high except for the line connected to the SPI device you wish to use at the time. Turtle Beach Santa Cruz Sound Card Driver. Data is sent to the SPI device in byte form. You should know by now that eight bits make one byte, therefore representing a binary number with a value of between zero and 2. When communicating with our SPI devices, we need to know which way the device deals with the data MSB or LSB first. MSB most significant bit is the left hand side of the binary number, and LSB least significant bit is the right hand side of the number. That is Apart from sending numerical values along the SPI bus, binary numbers can also represent commands. You can represent eight onoff settings using one byte of data, so a devices parameters can be set by sending a byte of data. These parameters will vary with each device and should be illustrated in the particular devices data sheet. For example, a digital potentiometer IC with six pots This device requires two bytes of data. The ADDR byte tells the device which of six potentiometers to control numbered 0 to 5, and the DATA byte is the value for the potentiometer 02. We can use integers to represent these two values. For example, to set potentiometer number two to 1. How do we send data to SPI devices in our sketches First of all, we need to use the SPI library. It is included with the default Arduino IDE installation, so put the following at the start of your sketch Next, in void. SS and set them as OUTPUT. For example. pin. Modess, OUTPUT where ss has previously been declared as an integer of value ten. Now, to activate the SPI bus and finally we need to tell the sketch which way to send data, MSB or LSB first by using. SPI. set. Bit. OrderMSBFIRST 1. SPI. set. Bit. OrderMSBFIRST or. SPI. set. Bit. OrderLSBFIRST 1. SPI. set. Bit. OrderLSBFIRST When it is time to send data down the SPI bus to our device, three things need to happen. First, set the digital pin with SS to low. WriteSS, LOW Then send the data in bytes, one byte at a time using. SPI. transfervalue Value can be an integerbyte between zero and 2. Finally, when finished sending data to your device, end the transmission by setting SS high. Writess, HIGH Sending data is quite simple. Generally the most difficult part for people is interpreting the device data sheet to understand how commands and data need to be structured for transmission. But with some practice, these small hurdles can be overcome. Now for some practical examples Time to get on the SPI bus and control some devices. By following the examples below, you should gain a practical understanding of how the SPI bus and devices can be used with our Arduino boards. Example 3. 4. 1. Our first example will use a simple yet interesting part a digital potentiometer we also used one in the I2. C tutorial. This time we have a Microchip MCP4. Here is the data sheet. To control it we need to send two bytes of data the first byte is the control byte, and thankfully for this example it is always zero as the address for the wiper value is 0. The second byte is the the value to set the wiper, which controls the resistance. So to set the wiper we need to do three things in our sketchFirst, set the SS slave select line to low. Write1. 0, LOW Then send the two byes of data. SPI. transfer0 command byte. SPI. transfervalue wiper value. SPI. transfer0 command byte. SPI. transfervalue wiper value. Finally set the SS line back to high. Write1. 0, HIGH Easily done. Connection to our Arduino board is very simple consider the MCP4. Vdd connects to 5. V, Vss to GND, CS to digital 1. SCK to digital 1. SDI to digital 1. SDO to digital 1. Now lets run through the available values of the MCP4. Example 3. 4. 1 SPI bus demo using a Microchip MCP4. Quality Unit Patch 2005 on this page. Dmnd. http tronixstuff. CC by sa nc John Boxall. SPI. h necessary library. SPI slave select. Modess, OUTPUT we use this for SS pin. SPI. begin wake up the SPI bus. SPI. set. Bit. OrderMSBFIRST. MCP4. 16. 2 requires data to be sent MSB most significant byte first. Valueint value. Writess, LOW. SPI. SPI. transfervalue send value 02. Writess, HIGH. for int a0 alt 2. Valuea. delaydel. Valuea. delaydel. Example 3. 4. 1 SPI bus demo using a Microchip MCP4. Dmnd http tronixstuff. CC by sa nc John Boxallinclude SPI. SPI slave selectintdel2. Modess,OUTPUT we use this for SS pin  SPI. SPI bus.   SPI. set. Bit. OrderMSBFIRST   our MCP4. MSB most significant byte firstvoidset. Valueintvalue  digital. Writess,LOW  SPI. SPI. transfervalue send value 02. Writess,HIGH voidloop  forinta0 alt 2. Valuea    delaydel    forinta2. Valuea    delaydel  Now to see the results of the sketch.