I2C Bus and SPI Interface - SC12 @CHIP-RTOS V1.10

I2C Bus / SPI API

Philips was the inventor of the Inter-IC or I²C-bus, and it is now firmly established as the worldwide de-facto solution for embedded applications. It is used extensively in a variety of microcontroller-based professional, consumer and telecommunications applications as a control, diagnostic and power management bus. As a two-wire serial bus, its inherently simple operation was crucial to its emergence as the worldwide de-facto standard.

SPI is a serial bus standard established by Motorola. The Serial Peripheral Interface (SPI) is a synchronous serial interface useful for communicating with other peripheral or microcontroller devices. These peripheral devices may be Serial EEPROMs, shift registers, display drivers, A/D converters, etc.

• I2C Bus / SPI API News

Interrupt 0xAA service 0x80: Initialize the I2C Bus

This function initializes the I2C bus. It enables the two defined PIO pins for I2C usage (see also function 8eh and 8fh).

Parameters

AH

0x80

Comments

The user can specify which two PIO are used for I2C clock and data.   After calling this initialization function, these two pins will no longer be available as PIO pins unless the PFE Enable function is called for these pins following this function call.

Related Topics

Select I2C Clock Pin

Select I2C Data Pin

PFE: Enable Programmable I/O Pins

Interrupt 0xAA service 0x81: Scan I2C Devices

Report addresses of slave devices, one at a time.

Parameters

AH

0x81

AL

First slave address (even address, LSB=0)

CL

Last slave address (even address, LSB=0)

Return Value

AL: 0 no slave found
AL: -1 Timeout
AL: address of the first found slave

Comments

This is an iterator function which is called repetitively to determine all connected slaves.   Specify on each successive call a new restricted slave address range until no further address is returned by this function.  

Interrupt 0xAA service 0x82: Transmit / Receive Character

Send or receive a single character.

Parameters

AH

0x82

AL

Slave address, LSB:0 => Transmit, LSB:1 => Receive

CL

If Transmit: CL = Byte to transmit
If Receive: CL = 0 for last char to be received

Return Value

Success: Carry flag cleared and CH contains received byte (if receiving)
Failure: Carry flag set and AL contains I2C error code

Comments

The IPC@CHIP is the I2C bus master.

The least significant bit of the slave address determines the direction of the communication.

Even address:   Master sending to slave
Odd address:   Master receiving from slave

If the direction or the slave address changes, this functions executes the I2C restart function automatically. This will insert a I2C start condition on the bus. After this, the I2C address is send again.

I2C error codes:

8: Timeout
9: Slave faulty or not available

Related Topics

I2C Transmit/Receive Block

Interrupt 0xAA service 0x83: Transmit/ Receive Block

Parameters

AH

0x83

AL

Slave address, LSB:0 => Transmit, LSB:1 => Receive

CX

Number of bytes to transmit or receive

ES:BX

Buffer address

Return Value

Success: Carry flag cleared
Failure: Carry flag set and AL contains I2C error code

Comments

If an odd slave address is specified in AL then this function will dwell here until either CX bytes are received and stored in user buffer at [ES:BX], or until an error occurs.   For an even slave address this function will dwell here until CX bytes from user buffer at [ES:BX] are transmit or until an error occurs.

If the direction or the slave address changes, this functions executes the I2C restart function automatically. This will insert a I2C start condition on the bus. After this, the I2C address is send again.

Related Topics

I2C Transmit/Receive Character

Interrupt 0xAA service 0x84: Release I2C Bus

Parameters

AH

0x84

Comments

This function generates an I2C stop condition. (The Bus will be released). At next call of transmit or receive functions, the address will be send again.

Interrupt 0xAA service 0x8b: Restart the I2C Bus

Parameters

AH

0x8b

Return Value

CF: 0

Comments

This function generates an I2C start condition. (The Bus will be reserved)

Interrupt 0xAA service 0x8E: Select I2C Clock Pin

Select IPC@CHIP I/O pin to be used for I2CCLK signal.

Parameters

AH

0x8E

AL

PIO pin number, [0..13]

Return Value

none

Comments

The default I2C clock pin is PIO 0
To change the I2CCLK pin this function must be called before the I2C initialize function (0x80) is called.

Related Topics

Initialize I2C Bus Function

Select I2C Data Pin

Interrupt 0xAA service 0x8F: Select I2C Data Pin

Select IPC@CHIP I/O pin to be used for I2CDAT signal.

Parameters

AH

0x8F

AL

PIO pin number, [0..13]

Return Value

none

Comments

The default I2C data pin is PIO 1
To change the I2CDAT pin this function must be called before the I2C initialize function (0x80) is called.

Related Topics

Initialize I2C Bus Function

Select I2C Clock Pin

Interrupt 0xAA service 0x90: SPI Init

Init the SPI Interface.

SPI specifies four signals: clock (SCLK); master data output, slave data input (MOSI); master data input, slave data output (MISO); and slave select (CSS). The slave select signal pin is not specified with the SPI init function and not activated with the SPI read and write functions. The user has to enable any other PIO pin for that purpose and should serve this pin manually.

Parameters

AH

Must be 0x90

BX

Mode, must be 0

CL

Pio number for SPI Clock Pin (SCLK)

CH

Pio number for SPI Input Pin (MISO)

DL

Pio number for SPI Output Pin (MOSI)

Return Value

none

Comments

none

Related Topics

Read SPI Block

Write SPI Block

Interrupt 0xAA service 0x95: SPI Write Block

Write n bytes out to the SPI Output pin

Parameters

AH

Must be 0x95.

ES:SI

Pointer to write buffer

CX

Number of bytes in buffer to write

Return Value

none

Comments

None

Related Topics

Init SPI

Read Block SPI

Interrupt 0xAA service 0x96: SPI Read Block

Reads n bytes from the SPI Input pin

Parameters

AH

Must be 0x96

ES:DI

Pointer to buffer for storing read data

CX

Number of bytes to read

Return Value

none

Comments

None

Related Topics

Init SPI

Write SPI Block

Interrupt 0xAA service 0x97: SPI Read and Write Block

Reads n bytes from the SPI Input pin and write n bytes out to the SPI Output pin simultaneously.

Parameters

AH

Must be 0x97

DS:DI

Pointer to buffer for storing read data

ES:SI

Pointer to buffer which stores write data

CX

Number of bytes to read and write

Return Value

none

Comments

None

Related Topics

Init SPI

Write SPI Block

Read SPI Block