Pic16f690 Serial Communication C Code Editor
Avs Video Editor Free Download No Watermark. Eurocodice 5 Legno Pdf Editor. Pic16f690 Serial Communication C Code Mustang. Hi-Tech C I2C Master Example Code. Here is some example code for a Microchip 12F1822 microcontroller which is setup as an I2C Master to communicate with one of our Servo.Pro chips (which is an I2C slave). Both read and write functions are used and it is written using the free Hi-Tech C compiler.
Become a subscriber (Free)Join 29,000 other subscribers to receive subscriber sale discounts andother free resources.Name:E-Mail:Don't worry - youre-mail address is totallysecure. I promise to use it only to send youMicroZine.I2C tutorial.This I2C tutorial shows you how the I2C protocol or more correctly writtenI 2C (sometimes written as IIC) stands for Inter IC Communication andis intended for very short distance communication between ICs on a single PCB.It gives you a fully defined protocol for data transfer between multipledevices over two wires.The great strength of the protocol is that it only requires two wires yetcan have many connected devices and all of these can transmit and receive dataat high speed. Unlike the SPI protocol the I2C protocol has an acknowledgementfeature that means a sending device knows that a receiver has accepted thedata. This means I2C is more robust when in a noisy environment.
For SPI thereis also no concept of multiple master devices but SPI is faster.Usually a master device sends out data to slaves (that give the ACK signal -a single bit returned at the end of transmission) but you can have more thanone master device in a system allowing great flexibility of use for I2C.In this I2C tutorial you will learn all about the 2 wireI2C serial protocol; How easy it is to use, how it works and when to use it.The I2C protocol is a very useful serial communication protocol. Thispopular system is used in a huge range of chips - just a few examples from thissite include the DS1307 (RTC), SSD1306 (OLED Display), DS23017 (Serialexpander). It allows you to connect many devices to a single set of two wiresand then communicate individually with each device with which you can send andreceive data. Warning: The protocol is designed for single boardcommunication it is not a long distance comms. You can find instances(horror stories) of people designing a multi drop inter office comms systemwith I2C extenders - just don't do it - it ends in tears!This I2C tutorial shows you how the I2C protocol works at the physical bitlevel discussing single master mode (a single controlling device) which is themost common use for I2C in a small system.Note: You can find Mastermode soft I2C routines in theproject.I2C Tutorial - Open drain connections.I2C works by using open drain connections. The two resistors above are thepull-up resistors that allow the whole system to work - when all devices areinactive then the 'pullups' pull the signal wire to the supply voltage. Warning: you must have one pullup resistor per signal wire(SCL and SDA) and not more!At any time a master device can start a transmission by pulling SDA lowwhile SCL is high (a unique specific condition that other I2C devices recogniseas the start of a master transmission).The slave device listens to the next 8 serial bits of the address to see ifit matches its own address (each I2C must have a unique address built in).
Ifit does recognise the next 8 bits as an address from the master device. Thenext bit tells the slave that it is to read or write data for the followingpacket. This is followed by the ACK bit that the slave must generate toindicate that it understood the address. The diagram further down shows this ingraphical form.When the ACK signal is to be generated the master device releases the SDAline and the open drain output is pulled high. This allows the slave device togenerate the ACK signal by pulling it low (only for that specific bitperiod). Note: Another protocol that uses the open - drain concept isthe Dallas 1-wire protocol - but that is far slower.
The advantage o the 1-wireprotocol is that it allows powering of the device through the signal wire! The1-wire protocol also allows transmission over very large distances unlike theI2C protocol. On this site this project ( ) uses the 1-wire protocol. Master and slaveThe phillips I2C protocol defines the concept of master andslave devices. A master device is simply the device that is in charge of thebus at the present time and this device controls the clock and generates STARTand STOP signals. Slaves simply listen to the bus and act on controls and datathat they are sent.The master can send data to a slave or receive data from aslave - slaves do not transfer data between themselves. Multi MasterMulti master operation is a more complex use of I2C that letsyou have different controlling devices on the same bus.
You only need to usethis mode if you have more than one microcontroller on the bus (and you wanteither of them to be the bus master).Multi master operation involves arbitration of the bus (where amaster has to fight to get control of the bus) and clock synchronisation (eachmay a use a different clock e.g. Because of separate crystal clocks for eachmicro).Note: Multi master is not covered in this I2C tutorial asthe more common use of I2C is to use a single bus master to control peripheraldevices e.g. Serial memory, ADC, RTC etc. Data and ClockThe I2C interface uses two bi-directional lines meaning thatany device could drive either line.
Note: Even if you run an I2C peripheral at a high speed theoverall data rate depends on how fast you can push data into the internal I2Cmodule and that depends on the processor speed.A slow slave device may need to stop the bus while it gathers data orservices an interrupt etc. It can do this while holding the clock line (SCL)low forcing the master into the wait state. The master must then wait until SCLis released before proceeding. Data transfer sequenceA basic Master to slave read or write sequence for I2C followsthe following order:. 1. Send the START bit (S).
2. Send the slave address (ADDR). 3.
Send the Read(R)-1 / Write(W)-0 bit. 4.
Wait for/Send an acknowledge bit (A). 5. Send/Receive the data byte (8 bits) (DATA). 6. Expect/Send acknowledge bit (A). 7.
Send the STOP bit (P).Note: You can use 7 bit or 10 bit addresses.The sequence 5 and 6 can be repeated so that a multibyte blockcan be read or written.Data Transfer from master to slaveI2C Tutorial: Instruction sequence data from master to slaveA master device sends the sequence S ADDR W and then waits for anacknowledge bit (A) from the slave which the slave will only generate if itsinternal address matches the value sent by the master. If this happens then themaster sends DATA and waits for acknowledge (A) from the slave. The mastercompletes the byte transfer by generating a stop bit (P) (or repeatedstart). Data transfer from slave to masterI2C Tutorial: Instruction sequence data from slave to masterA similar process happens when a master reads from the slave but in thiscase, instead of W, R is sent. After the data is transmitted from the slave tothe master the master sends the acknowledge (A). If instead the masterdoes not want any more data it must send a not-acknowledge which indicates tothe slave that it should release the bus.
This lets the master send the STOP orrepeated START signal. Device addressesEach device you use on the I2C bus must have a unique address.For some devices e.g. Serial memory you can set the lower address bits usinginput pins on the device others have a fixed internal address setting e.g. Areal time clock DS1307.
Asynchronous Serial Communication Pdf
You can put several memory devices on the same IC busby using a different address for each.Each device manufacturer is assigned a set of addresses so devices shouldnot conflict with each other.Note: The maximum number of devices is limited by the numberof available addresses (and you need non-conflicting addresses) and by thetotal bus capacitance (maximum 400pF). General callThe general call address is a reserved address which whenoutput by the bus master should address all devices which should respond withan acknowledge.Its value is 0000000 (7 bits) and written by the master0000000W.
If a device does not need data from the general call it does not needto respond to it. Reserved addresses0000 000 1 START byte - for slowmicros without I2C h/w0000 001 X CBUS address - a different bus protocol0000 010 X Reserved for different bus format0000 011 X Reserved for future purposes0000 1XX X Hs-mode master code1111 1XX X Reserved for future purposes1111 0XX X 10-bit slave addressingMost of these are not that useful for PIC microcontrollersexcept perhaps the START byte and 10 bit addressing. START (S) and STOP (P) bitsSTART (S) and STOP (P) bits are unique signals that can begenerated on the bus but only by a bus master.Reception of a START bit by an I2C slave device resets itsinternal bus logic. This can be done at any time so you can force a restart ifanything goes wrong even in the middle of communication.START and STOP bits are defined as rising or falling edges onthe data line while the clock line is kept high. I2C Tutorial: START and STOP Signal DefinitionSTART condition (S)SCL = 1,SDA falling edgeSTOP condition (P)SCL = 1,SDA rising edgeThe following diagram shows the above information graphically -these are the signals you would see on the I2C bus.I2C Tutorial: START (S) and STOP (P) bits. Note: In a single master system the only difference betweena slave and a master is the master's ability to generate START and STOP bits.Both slave and master can control SDA and SCL. Repeated START (Sr)This seems like a confusing term at first as you ask yourselfwhy bother with it as it is functionally identical to the sequence:S ADDR (R/W) DATA A PThe only difference is that for a repeated start you can repeatthe sequence starting from the stop bit (replacing the stop bit with anotherstart bit).S ADDR (R/W) DATA A Sr ADDR (R/W) DATA A Pand you can do this indefinitely.Note: Reception of both S or Sr force any I2C device resetits internal bus logic so sending S or Sr is really resetting all the busdevices.
This can be done at any time - it is a forced reset.The main reason that the Sr bit exists is in a multi masterconfiguration where the current bus master does not want to release itsmastership. Using the repeated start keeps the bus busy so that no other mastercan grab the bus.Because of this when used in a Single master configuration itis just a curiosity. DataAll data blocks are composed of 8 bits. The initial block has 7address bits followed by a direction bit (Read or Write). Following blocks have8 data bits. Acknowledge bits are squeezed in between each block.Each data byte is transmitted MSB first including the addressbyte.To allow START and STOP bit generation by the master the dataline (SDA) must not be changed while the clock (SCL) is high - it can only bechanged when the clock is low.
AcknowledgeThe acknowledge bit (generated by the receiving device)indicates to the transmitter that the the data transfer was ok. Note that theclock pulse for the acknowledge bit is always created by the bus master.The acknowledge data bit is generated by either the master orslave depending on the data direction. For the master writing to a slave (W)the acknowledge is generated by the slave. For the master receiving (R) datafrom a slave the master generates the acknowledge bit.Acknowledge0voltsNot acknowledgeHighvoltsACK data master - slaveIn this case the slave generates the acknowledge signal.When a not-acknowledge is received by the bus master thetransfer has failed and the master must generate a STOP or repeated START toabort the sequence.
ACK data slave - masterIn this case the master generates the acknowledge signal.Normally the master will generate an acknowledge after it hasreceived data but to indicate to the slave that no more data is required on thelast byte transfer the master must generate a 'not-acknowledge'. This indicatesto the slave that it should stop sending data. The master can then generate theSTOP bit (or repeated START). General CallThe general call function is a specialised command that must be accepted byall devices on the bus.
Data Framing In Serial Communication
It allows a master device to communicate to all devicesat the same time - giving them some data. Perhaps you would use this to commanda software reset in the case of a watchdog timeout in the processor. I2C Tutorial: Specifics for the 16F88 Pin configurationTo use the I2C mode in the 16F88 the SDA and SCL pins must beinitialised as inputs (TRIS bit = 1) so that an open drain effect is created.By setting them as inputs they are not driving the wires and an external pullup resistor will pull the signals high. 16F88 Slave modeThe 16F88 fully implements all slave functions except generalcall. Full slave modeThe general call function does not really matter as it is quitespecialised commanding all devices on the bus to use some data.A low output is generated by driving the signal line low andchanging the pin direction to an output. A high output is generated by changingthe pin direction to an input so that the external resistor pulls the signalhigh.In slave mode this action is done for you by the SSP module(the outputs of the register at SDA and SCL are driven low automatically -regardless of the state of the register value). 16F88 Master modeBasically there is very limited master mode functionality.There are two elements that are provided:.
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Interrupts. Pin control16F88 InterruptsThere are two interrupts that activate on reception of either aSTART or STOP condition. These two interrupts are only useful in a multi mastermode system where it is necessary for the non-master device to detect the startand stop conditions. So for a single master system they are of no use atall!
16F88 Pin controlNote When the SSP module is active SDA and SCL output arealways set at zero regardless of the state of the register values. So all youhave to do is control the port direction.In master mode (16F88) SDA and SCL must be controlled usingsoftware. I2C Tutorial: Specifics for 16F877AIt does it all for you!.
Full master mode. Full slave mode. Full general call.Note: If you want a chip with full master and slave modeoperation look for the MSSP module in a PIC chip e.g. 16F877A - then you won'tneed more software - just enough to drive the module. PIC Project ExamplesReal time clock (bit bangedI2C). Arduino Projects ExamplesPressure sensorIO expander.Jump fromtoBest-microcontroller-projects home pageShow Index.