serial communicationsjmconrad/ecgr4101-2012-01/...serial communications – rs232 standard – uart...

1Embedded Systems

Serial Communications

Embedded Systems 2

In these notes . . .

General CommunicationsSerial Communications

– RS232 standard– UART operation– Polled Code– SCI/I2C

A

A

B

B

C

C

D

D

E

E

4 4

3 3

2 2

1 1

RSR/WVo

E

DB4DB7 DB6

NOTE: All resistors are 0.1 W, 5%, unless designated otherwise

DB5

Voltage SelectOPEN: 5.0VCLOSED: 2.5-5.0V

fromUART1 connector

GND9VDCpositive center

VCC

EXTPower

POWER

UART 0:RS-232C

Contrast

LCD module

MANUALRESET

AN0KI1KI2KI3

* open JP3 to use internal ring oscillator

UART 1:Debug port

to 50-pinconnector

to 50-pinconnector

to 50-pinconnector

to 50-pinconnector

frequency

UP = IODOWN = LEDs

to 50-pinconnector

AN1

SCLKCE*

READYRxD

TxD

MCUPower

Vref

EXT OSC

CNVss

UP = IODOWN = XC

UP = RC_OSCDOWN = XTAL

UP = IODOWN = RS232

MDECE30262 1.1

MDECE30262 Board Rev A

C

1 1Tuesday, October 01, 2002

Mitsubishi Electric & Electronics US

Title

Size Document Number Rev

Date: Sheet of

P7_2

P10_7

P7_1

Vref

P10_6 P10_5

RESET*

P9_0P9_1P9_2P9_3

P6_0

P7_0

P8_0

P10_0

P6_1

P7_1

P8_1

P6_2

P7_2

P8_2

P6_3

P7_3

P8_3

P6_4

P7_4

P6_5

P7_5

P8_5

P6_6

P7_6

P8_6

P6_7

P7_7

P8_7

P10_1P10_2P10_3P10_4P10_5P10_6P10_7

P1_5P1_6P1_7

P10_0P10_1P10_2P10_3P10_4P10_5P10_6P10_7

P1_5P1_6P1_7

P9_0P9_1P9_2P9_3

P6_0

P7_0

P8_0

P6_1

P7_1

P8_1

P7_2

P8_2

P6_2MP6_3M

P7_3

P8_3

P7_4

P6_4P6_5

P8_5

P7_5

P8_6M

P6_6

P7_6

P6_7

P8_7M

P7_7

P8_6

P8_7

P8_6M

P8_7M

P6_3

P6_2

P6_3M

P6_2M

P1_6P1_7

P7_5P7_7 P7_6

P7_4

RESET*

RESET*P6_7

P8_6P6_5

P6_4

RESET*

P10_0P10_1

Vref

P7_0

P6_6

VCC

VCC VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

VCC

R1910K

12

R2010K

12

R24680

12

R25680

12

R26680

12

Z1

FIDUCIAL

J4

POWER JACK

Tip 1

O 2

O 3+

C2010uF

TB1

RED

1

TB2

BLACK

1

U5LM317M

VIN3

AD

J1

VOUT 2

D7GREEN

12

JP51 2

JP71 2

+C1847uF

+ C74.7uF 16V

S1EVQ-PAC04M

D2FMMD914CT

13

Y220MHz

1 2 3

JP61 2

C1

0.1uF

1 2C3

0.1uF

12

C5

20pF

12C4

20pF

1 2

MH4

MTG_HOLE

C14

0.1uF

1 2

C17

0.1uF

12C13

0.1uF

1 2

C16

0.1uF

12

Vcc V+C1+ C2+

C2-C1-

GND V-

T

R

T

R

U4

MAX202/3232

12

3

4

5

6

7

89

10

11

12 13

14

15

16

MH3

MTG_HOLE

MH2

MTG_HOLE

MH1

MTG_HOLE

P1

747250-4

594837261

C11

0.1uF

1 2

Z2

FIDUCIAL

Z3

FIDUCIAL

Z4

FIDUCIAL

Z5

FIDUCIAL

Z6

FIDUCIAL

C10

33pF

12C8

33pF

1 2

t

RT1RL0503-5820-97-MS

12

J1

25x2 Connector

1 23 45 67 89 1011 1213 1415 1617 1819 2021 2223 2425 2627 2829 3031 3233 3435 3637 3839 4041 4243 4445 4647 4849 50

J2

103308-1

+1

+3

+5

+7

+9

+ 2

+ 4

+ 6

+ 8

+ 10

C190.1uF

12

C210.1uF

12

C60.1uF

12

C933pF

12

C150.1uF

12

D3RED

12

D4YELLOW

12

D5GREEN

12

S2EVQ-PAC04M

S3EVQ-PAC04M

S4EVQ-PAC04M

R41301 1%

12

R44432 1%

12

R37.32K 1%

12

R1510K

12

R162.2K

12

R42.2K

12

R52.2K

12

R710K

12

R1310K

12

R2310K

12

R43680

12

R1410K

1 2

R1100K

1 2

U3

ACM0802B

12345678910

11121314

A15 C16

C2

0.1uF

12

R2210K

13

2

R1750K

13

2

R462K

13

2

R2110K

12

JP1

12

C220.1uF

12

JP2

1 2

TB3

HOLE

1

TB4

HOLE

1

TB5

HOLE

1

TB6

HOLE

1

R1850K

13

2

R45

909 1%

12

Y1

32.768KHz

1 4

U1

M30262

AVss44

P15/INT3/ADtrg36

P16/INT435

P17/INT534

P60/CTS0/RTS0 33

P61/CLK0 32

P62/RxD0 31

P63/TxD0 30

P64/CTS1/RTS1 29

P65/CLK1 28

P66/RxD1 27

P67/TxD1 26

P70/TxD2/TA0out 25

P71/RxD2/TA0in 24

P72/CLK2/TA1out/V 23

P73/CTS2/RTS2/TA1in/V 22

P74/TA2out/W 21

P75/TA2in/W 20

P76/TA3out 19

P77/TA3in 18

P80/TA4out/U 17

P81/TA4in/U 16

P82/INT0 15

P83/INT1 14

P85/NMI 12

P86/Xcout 6

P87/Xcin 5

P90/TB0in 3

P91/TB1in 2

P92/TB2in 1

P93 48

P100/AN045

P101/AN143

CNVss4

P102/AN242

P103/AN341

P104/AN4/KI040

P105/AN5/KI139

P106/AN6/KI238

P107/AN7/KI337

Vss9

Vref46

AVcc47

Vcc11

Xin10

Xout8

RESET7

VDC13

JP31 2

Rx10K

12

S5ACT204222ST

116

15

314

13

2

4

S5B

CT204222ST

5 12

11

7 10

9

6

8

S6BCT204222ST5 12

11

7 10

9

6

8

S6ACT204222ST1 16

15

3 14

13

2

4

Mitsubishi microcomputers M16C/26 Group

SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER Serial I/O

108

Under

development Preliminary Specifications Rev.0.30 Specifications in this manual are tentative and subject to change.

Figure 1.15.2. Block diagram of UARTi (i = 0, 1) transmit/receive unit

SP SP PAR

2SP

1SP

UART

UART (7 bits)UART (8 bits)

UART (7 bits)

UART (9 bits)

Clock synchronous type


TxDiUARTi transmit register

PAR enabled

PAR disabled

D8 D7 D6 D5 D4 D3 D2 D1 D0

SP: Stop bitPAR: Parity bit

UARTi†transmit buffer register

MSB/LSB conversion circuit



UARTi receive buffer register

UARTi receive register

2SP

1SP

PAR enabled

PAR disabled

UART

UART (7 bits)

UART (9 bits)




RxDi



Address 03A616Address 03A716Address 03AE16Address 03AF16

Address 03A216Address 03A316Address 03AA16Address 03AB16

Data bus low-order bits

MSB/LSB conversion circuit

D7 D6 D5 D4 D3 D2 D1 D0D80 0 0 0 0 0 0

SP SP PAR

0

Data bus high-order bits

Embedded Systems 3

There was no standard for networks in the early days and as a result it was difficult for networks to communicate with each other.

The International Organization for Standardization (ISO) recognized this and in 1984 introduced the Open Systems Interconnection (OSI) reference model.

The OSI reference model organizes network functions into seven numbered layers.

Each layer provides a service to the layer above it in the protocol specification and communicates with the same layer’s software or hardware on other computers.

Layers 5-7 are concerned with services for the applications.

Layers 1-4 are concerned with the flow of data from end to end through the network

Data Communications

Embedded Systems 4

Physical Layer (1) – Serial CommunicationsThe basic premise of serial communications is that one or

two wires are used to transmit digital data.– Of course, ground reference is also needed (extra wire)

Can be one way or two way, usually two way, hence two communications wires.

Often other wires are used for other aspects of the communications (ground, “clear-to-send”, “data terminal ready”, etc).

Tx

TxRx

RxMachine 1 Machine 2

101101100111

001101101111

Embedded Systems 5

Serial Communication Basics

Send one bit of the message at a time

Message fields– Start bit (one bit)– Data (LSB first or MSB, and size – 7, 8, 9 bits)– Optional parity bit is used to make total number of ones in data even or odd– Stop bit (one or two bits)

All devices on network or link must use same communications parameters – The speed of communication must be the same as well (300, 600, 1200, 2400,

9600, 14400, 19200, etc.)More sophisticated network protocols have more information in each message

– Medium access control – when multiple nodes are on bus, they must arbitrate for permission to transmit

– Addressing information – for which node is this message intended?– Larger data payload– Stronger error detection or error correction information– Request for immediate response (“in-frame”)

Message

Databits

Embedded Systems 6

Bit Rate vs. Baud Rate

Bit Rate: how many data bits are transmitted per second?Baud Rate: how many symbols are transmitted per second?

– == How many times does the communication channel change state per second?

– A symbol may be represented by a voltage level, a sine wave’s frequency or phase, etc.

These may be different– Extra symbols (channel changes) may be inserted for framing, error

detection, acknowledgment, etc. These reduce the bit rate– A single symbol might encode more than one bit. This increases the

bit rate.• E.g. multilevel signaling, quadrature amplitude modulation, phase

amplitude modulation, etc.

Embedded Systems 7

Serial Communication BasicsRS232: rules on connector, signals/pins, voltage levels, handshaking, etc.RS232: Fulfilling All Your Communication Needs, Robert AshbyQuick Reference for RS485, RS422, RS232 and RS423Not so quick reference:The RS232 Standard: A Tutorial with Signal Names and Definitions, Christopher E. StrangioBit vs Baud rates: http://www.totse.com/en/technology/telecommunications/bits.html

Embedded Systems 8

UART ConceptsUART

– Universal – configurable to fit protocol requirements– Asynchronous – no clock line needed to de-serialize bits – Receiver/Transmitter

Embedded Systems 9

RS232 Communications CircuitExample RS-232 buffer (level-shifting) circuit

Max202/3232 includescharge pump to generate+10 V and -10V from single 5V supply

Logic-level signals(Vcc or Ground)

RS232-level signals(> 3 V or < -3 V)

Embedded Systems 10

General UART ConceptsUART subsystems

–Two fancy shift registers• Parallel to serial for

transmit• Serial to parallel for

receive–Programmable clock source• Clock must run at 16x

desired bit rate–Error detection

• Detect bad stop or parity bits

• Detect receive buffer overwrite

–Interrupt generators• Character received• Character

transmitted, ready to send another

Block Diagram of RX62N Serial Comm Interface

Embedded Systems 11

SCI in UART ModeTo communicate from the RX62N chip, you need to set up several registers, including:• Mode• Speed• Parity• Stop bits• Configuration

Embedded Systems 12

There are two primary “Data Registers”• SCIx.RDR (Receive Data Register)• SCIx.TDR (Transmit Data Register)

Serial Mode Register (SMR)

SCIx.SMR – Operational values of the UART

Each bit is encoded to make a special meaningCKS: transmission speed (more later)MP: Multi processor (set to 0)STOP: Stop bitsPM: Parity modePE: Parity EnableCHR: Length of dataCM: Communications mode

Embedded Systems 13

Reading a Manual (SMR)

Embedded Systems 14

Embedded Systems 15

Setting up the Serial Control Register

We will use SCI0There are several “control” registers you need to set up

before you can communicate.– First, you need to set up the speed of your port.– Select 8 data bits, no parity, one stop bit (8N1)– Asynchronous mode

What would the byte be set as?

SCI0.SMR.BYTE =

Serial Control Register

Embedded Systems 16

Serial Control Register – Serial Status Register

Check to see is communications was successful (SCIx.SSR)

Embedded Systems 17

Identifying Errors

char read_sci0_status;read_sci0_status = SCI0.SSR.BYTE;

What does it mean if the value holds 0x04?

What does it mean if the value holds 0x0C?



Embedded Systems 18

Embedded Systems 19

Setting up Speed of the Serial Port

The speed of communications is a combination of• PCLK• Bits CKS in the SMR• The Bit Rate Register (BRR)

Based on formula:B=bit rate, N=BRR setting, n=CKS setting

So, if you want to communicate at 38,400 bps, if your PCLK is 50 MHz, set n=0 and N=40

SCI0.BRR.BYTE = 40;

Embedded Systems 20

Example – Change to Slower Clock

What about a slower clock?

Say, 2400 bps? What do you need to set n and N?

Class Exercise – Set up clock

Set up to 115,200, including writing the code for BRR.

Embedded Systems 21

Error rate

The error rate is associated to the settings of n and N, since you will not get the exact value of xx.0.

So, if you want to communicate at 38,400 bps, if your PCLK is 50 MHz, set n=0 and N=40, error is:

Embedded Systems 22

What is the Maximum Speed??

Embedded Systems 23

Embedded Systems 24

Example – Set up Communications

Write a function to set up SCI0 to 115,200 bps, 8 data bits, odd parity, 1 stop bit:

Example – Send/receive data

Write a small function to send the string “Sending data” through the SCI0 port. Make sure to wait for the previous char to be transmitted before you send the next char:

Embedded Systems 25

Embedded Systems 26

Serial Communications and InterruptsNow we have three separate threads of control in the program

– main program (and subroutines it calls)

– Transmit ISR – executes when UART is ready to send another character

– Receive ISR – executes when UART receives a character

Need a way of buffering information between threads

– Solution: circular queue with head and tail pointers

– One for tx, one for rx

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Embedded Systems 27

Code to Implement QueuesEnqueue at tail (tail_ptr points to next free entry), dequeue from head (head_ptr points to item to remove)#define the queue size to make it easy to changeOne queue per direction

– tx ISR unloads tx_q– rx ISR loads rx_q

Other threads (e.g. main) load tx_q and unload rx_qNeed to wrap pointer at end of buffer to make it circular, use % (modulus, remainder) operatorQueue is empty if size == 0Queue is full if size == Q_SIZE

tailhead

older data

newer data

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Embedded Systems 28

Defining the Queues��

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Embedded Systems 29

Initialization and Status Inquiries,#��&�-�)��,#��&�-�)��,#��&�-�)��,#��&�-�)��

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Embedded Systems 30

Enqueue and Dequeue""�� )��""�� )��""�� )��""�� )��7777 8�$$��5��9:;&��;�8�$$��5��9:;&��;�8�$$��5��9:;&��;�8�$$��5��9:;&��;�7777 ��#��)��#��)��#��)��#��)�� )��&�-�)+�� )��&�-�)+�� )��&�-�)+�� )��&�-�)+��

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Serial Peripheral Interface (SPI)

• SPI bus is a de facto standard developed byMotorola

• Can work with as few as three wires, but more needed to access additional devices

• Better method to access peripherals than parallel I/O.

• Common clock means you can transmit at 25.0 Mbps

• Intended for very short distances (i.e. on-board)

• The RX62N has two SPI masters

Embedded Systems 31

SPI Details

•Serial Clock – RSPCK•Master Out, Slave in – MOSI (transmission from RX62N)•Master In, Slave Out – MISO (transmission from peripheral)•Slave Select – SSLx (select one of the peripheral devices)We will not investigate Multiple Master modes

Embedded Systems 32

SPI registers

• Serial Peripheral Control Register (SPCR)• Serial Peripheral Control Register 2 (SPCR2)• Serial Peripheral Pin Control Register (SPPCR) – set to

0x00• Slave Select Polarity (SSLP)• Serial Peripheral Status (SPS)

• Serial Peripheral Data Register (SPDR)

Embedded Systems 33

Serial Peripheral Control Register (SPCR)

Embedded Systems 34

Serial Peripheral Control Register 2 (SPCR2)

Slave Select Polarity (SSLP) – set these to 0 (active low)

Embedded Systems 35

Serial Peripheral Bit Rate Register (SPBR)

8 Bit value, used with SPCR

Embedded Systems 36

Serial Peripheral Command Register (SPCMDx)

Embedded Systems 37

Serial Peripheral Command Register (SPCMDx)

Embedded Systems 38

Serial Peripheral Status (SPS)

Embedded Systems 39

Code to set up SPI

void Init_RSPI(void){

MSTP(RSPI0) = 0;

IOPORT.PFGSPI.BIT.RSPIS = 0;

PORT.PFGSPI.BIT.RSPCKE = 1;

IOPORT.PFGSPI.BIT.SSL3E = 0;

IOPORT.PFGSPI.BIT.MOSIE = 1;

PORTC.DDR.BIT.B4 = 1;

PORTC.DR.BIT.B4 = 1;







RSPI0.SPPCR.BYTE = 0x00;

RSPI0.SPBR.BYTE = 0x00;

RSPI0.SPDCR.BYTE = 0x00;

RSPI0.SPCKD.BYTE = 0x00;

RSPI0.SSLND.BYTE = 0x00;

RSPI0.SPND.BYTE = 0x00;

RSPI0.SPCR2.BYTE = 0x00;

RSPI0.SPCMD0.WORD = 0x0700;

RSPI0.SPCR.BYTE = 0x6B;

RSPI0.SSLP.BYTE = 0x08;

RSPI0.SPSCR.BYTE = 0x00;

}

Embedded Systems 40

Code to communicate via SPI

void RSPI_Transmit_LWord(int16_t sLowWord, int16_t sHighWord){


while (RSPI0.SPSR.BIT.IDLNF);

RSPI0.SPDR.WORD.L = sLowWord;

RSPI0.SPDR.WORD.H = sHighWord;

while (RSPI0.SPSR.BIT.IDLNF);

(void)RSPI0.SPDR.WORD.L;

(void)RSPI0.SPDR.WORD.H;

PORTC.DR.BIT.B4 = 1 ; //CS OFF

}

Embedded Systems 41

I2C

Inter-Integrated Circuit Bus

•A two line bus for communicating data at high speeds•Multiple devices on the same bus with only one master controlling the bus•Needs pull up resistors and is kept at a digital high level when idle

Embedded Systems 42

Device 1Address (0x80)

Device 2Address (0xC0)

Device 3Address (0xE1)

Device 4Address (0x70)

SCL

SDA

Vcc

I2C: Properties

Modes

Max Transfer Speed

Max. number of devices/slaves connected per busNumber of wires required for communication (not including ground)Max. Length of wires[6]

Number of bits per unit transfer (excluding start and stop)Slave Selection method

Renesas Inter Integrated Chip Bus

I2C mode or SM bus mode

Up to 1Mbps (most devices won’t support speeds beyond 400kbps)128 (0 to 27 bits-1)

2

10 meters @ 100kbps

8

Through addressing

Embedded Systems 43

I2C: Working

Two wires:• SCL (Serial Clock): Synchronizing data transfer

on the data line • SDA (Serial Data): Responsible for transferring

data between devices• Together they can toggle in a controlled fashion

to indicated certain important conditions that determine the status of the bus and intentions of the devices on the bus.

Embedded Systems 44

I2C: Working (Contd …) START CONDITION

• Before any form of data transfer takes place, a device wanting to transfer data must take control of the bus (Needs to monitor the bus).

• If the bus is held high, then it is free. A device may issue a START condition and take control of the bus.

• If a START condition is issued, no other device will transmit data on the bus (predetermined behavior for all devices).

Embedded Systems 45

START

I2C: Working (Contd …) STOP CONDITION

• When device is ready to give up control of the bus, it issues a STOP condition

• STOP condition is one in which the SDA line gets pulled high while the SCL line is high.

• Other conditions: RESTART (combination of a START and STOP signal)

Embedded Systems 46

STOP

I2C: Working (Contd …) After START

• Address the slave device with one byte of data which consists of a 7 bit address + 1 bit (R/W)

• If this bit is low, it indicates that the master wants to write to the slave device; if high, the master device wishes to read from the slave. This determines whether the next transactions are going to be read from or written to the addressed slave devices.

• A ninth bit (clock) is transmitted with each byte of data transmitted (ACK(Logic 0)/NACK(logic 1) bit). The slave device must provide an ACK within the 9th cycle to acknowledge receipt of data

Embedded Systems 47

For Real???? Let’s have a look ..

Embedded Systems 48

START

7 bit address(0x3A) R/W bit

ACK STOP

I2C: Code: Simple example (START and STOP)void RiicIni(unsigned char in_SelfAddr){

SYSTEM.MSTPCRB.BIT.MSTPB21 = 0;

RIIC0.ICCR1.BIT.ICE = 0;

RIIC0.ICCR1.BIT.IICRST = 1;

RIIC0.ICCR1.BIT.IICRST = 0;

RIIC0.SARU0.BIT.FS = 0;

RIIC0.SARL0.BYTE = in_SelfAddr;

RIIC0.ICMR1.BIT.CKS = 7;

RIIC0.ICBRH.BIT.BRH = 28;

RIIC0.ICBRL.BIT.BRL = 29;

RIIC0.ICMR3.BIT.ACKWP = 1;

RIIC0.ICIER.BIT.RIE = 1;

RIIC0.ICIER.BIT.TIE = 1;

RIIC0.ICIER.BIT.TEIE = 0;

RIIC0.ICIER.BIT.NAKIE = 1;

RIIC0.ICIER.BIT.SPIE = 1;

RIIC0.ICIER.BIT.STIE = 0;

RIIC0.ICIER.BIT.ALIE = 0;

RIIC0.ICIER.BIT.TMOIE = 0;

PORT1.ICR.BIT.B3 = 1;

PORT1.ICR.BIT.B2 = 1;

RIIC0.ICCR1.BIT.ICE = 1;

}

void RiicUnIni(void){

SYSTEM.MSTPCRB.BIT.MSTPB21 = 1;

}

unsigned char RiicSendStart(void){

if(RIIC0.ICCR1.BIT.ICE){

while(RIIC0.ICCR2.BIT.BBSY);

RIIC0.ICCR2.BIT.ST=1;

while(!(RIIC0.ICCR2.BIT.BBSY&&RIIC0.ICSR2.BIT.START));

RIIC0.ICSR2.BIT.START=0;

return 1;

}

else return 0;

}

unsigned char RiicSendStop(void){

if(RIIC0.ICCR1.BIT.ICE){

while(RIIC0.ICCR2.BIT.BBSY){

RIIC0.ICCR2.BIT.SP=1;

}

return 1;

}

else return 0;

}

Embedded Systems 49

I2C Code: Reading and writing ….unsigned char RiicReadByte(unsigned char

slave_addr, unsigned char slave_register_num){

RiicWriteByte(slave_addr,slave_register_num);

RiicSendStop();

RIIC0.ICSR2.BIT.STOP=0;

RiicSendStart();

while(!RIIC0.ICSR2.BIT.TDRE);

RIIC0.ICDRT=slave_addr|(0x01);

while(!RIIC0.ICSR2.BIT.RDRF);

if(RIIC0.ICSR2.BIT.NACKF==0){

RIIC0.ICMR3.BIT.WAIT=1;

RIIC0.ICMR3.BIT.ACKBT=1;

read_byte=RIIC0.ICDRR;

while(!RIIC0.ICSR2.BIT.RDRF);

RIIC0.ICSR2.BIT.STOP=0;

RIIC0.ICCR2.BIT.SP=1;

read_byte=RIIC0.ICDRR;

while(!RIIC0.ICSR2.BIT.STOP);

return read_byte;

}

else return 0xFF;

}

unsigned char RiicWriteByte(unsigned char slave_addr, unsigned char data_byte){

RIIC0.ICDRT=slave_addr&(0xFE);


RIIC0.ICDRT=data_byte;

while(!RIIC0.ICSR2.BIT.TEND){

if(RIIC0.ICSR2.BIT.NACKF){

RIIC0.ICSR2.BIT.NACKF=0;

return 0;

}

}


while(!RIIC0.ICSR2.BIT.TEND) {

if(RIIC0.ICSR2.BIT.NACKF){

RIIC0.ICSR2.BIT.NACKF=0;

return 0;

}

}

return 1;

}

Embedded Systems 50

I2C Code: the Glorious main()void main(void){

RiicIni(0x10);

RiicSendStart();

RiicWriteByte2(0x3A,0x2D,0x00);

RiicSendStop();

RiicSendStart();

i=RiicReadByte(0x3A,0x00);

RiicSendStop();

RiicUnIni();

while(1);

}

Embedded Systems 51

serial communicationsjmconrad/ecgr4101-2012-01/...serial communications – rs232 standard – uart...

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