PCA6408 - 8-bit I2C-bus I/O expander
Description
Library for interfacing NXP PCA6408A 8-bit I2C-bus I/O expander with interrupt output
The PCA6408A is a 8-bit general purpose I/O expander that provides remote I/O expansion for most microcontroller families via the I²C-bus interface. -) I2C interface with communication speed up to 400 kHz -) Two user selectable addresses (chosen by chip pin) -) Built-in level shiffter -) Interrupt output for indicating that an input state has changed
OVERVIEW
PCA6408_Abstract:
This library can be used to handle NXP PCA6408A type 8-bit general purpose I/O expander.
Interfaces:1x I2C 1x IRQ (optional)
The PCA6408A is an 8-bit general purpose I/O expander that provides remote I/O expansion for most microcontroller families via the I2C-bus interface.I2C interface with communication speed up to 400 kHz Two user selectable addresses (chosen by chip pin) Built-in level shifter Interrupt output for indicating that an input state has changed
For more information, see the NXP website
PCA6408_How_to_use:
/* Hardware setup */
const
{
PORT_I2C = 0, // The first I2C interface should be used.
CHIP_ADDR = PCA6408_I2C_ADR1, // I2C Address of the chip
// (depends on the logic level at the chip's ADDR pin)
}
/* Handles for available sensors */
new hPCA6408[TPCA6408_Handle]; // Handle to manage the PCA6408
/**
* Function that is called up when the device has been prepared for the start of the application by the
* "salve" function. I.e. the device is ready for proceeding with the application.
*/
#callback Basic_Test()
{
// Inits the I2C interface
catch(rM2M_I2cInit(PORT_I2C, PCA6408_CLOCK, 0));
// Inits PCA6408 (P0=Input, all other IOs configured as output with state LOW)
catch(PCA6408_Init(hPCA6408, PORT_I2C, CHIP_ADDR, PCA6408_BITMASK(0), 0x00));
// Sets P1=high
catch(PCA6408_Write(hPCA6408, 0x02));
// Reads and outputs inputs
new iReadValue;
catch(PCA6408_Read(hPCA6408, iReadValue));
#log("Inputs: %02X", iReadValue);
// Closes the I2C interface
catch(rM2M_I2cClose(PORT_I2C));
}
/* Application entry point */
main(){
salve(Basic_Test);
}
BASIC
PCA6408_CLOCK -
typical I2C clock speed to be used
PCA6408_I2C_ADRx:
Available PCA6408 I2C addresses
PCA6408_I2C_ADR0 - Must be used if ADDR Pin is "Low" (logic 0)
PCA6408_I2C_ADR1 - Must be used if ADDR Pin is "High" (logic 1)
PCA6408_Init(handle[TPCA6408_Handle], i2c, addr, input, output)
Initializes i2c communication with the PCA6408, sets the direction of the I/O pins and sets the outgoing logic levels of the pins defined as outputs
handle : TPCA6408_Handle - Empty device handle for a PCA6408
i2c : s32 - I2C interface where PCA6408 is connected to
The I2C interface must be initialized before using rM2M_I2cInit().
addr : s32 - I2C Address of the chip (depends on the logic level at the chip's ADDR pin)
Use only the addresses specified under PCA6408_I2C_ADRx
input : s32 - Direction of the I/O pins (Bit0 = P0, ..., Bit7 = P7)
0 - Output
1 - Input
output : s32 - Outgoing logic levels of the pins defined as outputs (Bit0 = P0, ..., Bit7 = P7)
0 - "Low"
1 - "High"
Bit values have no effect on pins defined as inputs.
returns : s32
OK - If successful
< OK - if an error occurs
PCA6408_BITMASK(pin)
Helper macro to convert pin to a bitmask
pin : s32 - Pin number 0-7
returns : s32 - 8-bit bitmask
PCA6408_Read(handle[TPCA6408_Handle], &val, iRegister=PCA6408_CMD_INPUT_PORT)
Read PCA6408 register
The function reads from the specified register and returns the read value.
handle : TPCA6408_Handle - Device handle of a specific PCA6408 (Initialized by PCA6408_Init() )
val : s32 - Buffer for storing the read value
1 - "High"
0 - "Low"
Polarity inversion registers allow polarity inversion of pins defined as inputs. Polarity inversion is not enabled by this library. However, you can use the PCA6408_Com() function to enable polarity inversion.
0 - "Low"
1 - "High"
1 - pin’s polarity is inverted
0 - pin’s original polarity is retained
0 - Output
1 - Input
iRegister : s32 - Register from which the data should be read
Use only the registers specified under PCA6408_CMD_x
returns : s32
OK - If successful
ERROR_PARAM - Register address is invalid
< OK - if an error occurs
PCA6408_Write(handle[TPCA6408_Handle], value)
Writes the logic levels to be set for the outputs pins to the output port register of the PCA6408
handle : TPCA6408_Handle - Device handle of a specific PCA6408 (Initialized by PCA6408Init() )
value - Logic levels to be set (Bit0 = P0, ..., Bit7 = P7)
0 - "Low"
1 - "High"
Bit values have no effect on pins defined as inputs.
returns : s32
OK - If successful
< OK - if an error occurs
PCA6408_IrqInit(irq, callback)
Enable IRQ handling
irq : s32 - Number of the interruptible pin (ranging from 0 for the first IRQ pin of the device up to WATCH_COUNT-1)
callback : TonWatch - Function that should be executed in the event of an interrupt
Type of function: #callback func(pinstate);
The interrupt is generated (falling edge on the PCA6408 INT pin) if any of the inputs changes. It is recommended to use PCA6408_Read within the
callback function to get the current input state.
PCA6408_IrqClose(irq)
Disable IRQ handling
irq : s32 - Number of the interruptible pin (ranging from 0 for the first IRQ pin of the device up to WATCH_COUNT-1)
EXPERT
PCA6408_CLOCK_MAX -
absolute maximum I2C clock speed
PCA6408_CMD_x:
Available commands/registers (Command | R/W | Default | Description
PCA6408_CMD_INPUT_PORT - | r | undefined | Input port register
PCA6408_CMD_OUTPUT_PORT - | r/w | 0xFF | Output port register
PCA6408_CMD_POLARITY - | r/w | 0x00 | Polarity inversion register
PCA6408_CMD_CONFIG - | r/w | 0xFF | Configuration register
PCA6408_Com(handle[TPCA6408_Handle], aData{}, writelen, readlen)
Performs raw PCA6408 read/write access. Data is first of all sent and data is then received.
handle : TPCA6408_Handle - Device handle of a specific PCA6408 (Initialized by PCA6408_Init() )
aData : {} - Array in which the data to be sent must initially be saved. Once the data has been sent, the array is used as a memory for the data to be received.
writelen : s32 - Number of bytes to be sent
readlen : s32 - Number of bytes to be received
returns : s32
OK - if successful
< OK - if an error occurs
Access to PCA6408 is always started by sending one byte command code (see PCA6408_CMD_x definitions) followed by one byte read/write data.
Please see datasheet for more information
DEBUG
PCA6408_Debug_Config:
To configure debug mode add the following macro to the main.dde file.
/**
* Use this macro to configure the debug mode:
*
* 0: No debugging
* >0: Issues the following information via the console:
* -) I2C address used to access the PCA6408
* -) When initializing: direction of the I/O pins and Outgoing logic
* levels of the pins defined as outputs
* -) The content of the register is output when calling PCA6408_Read
* -) The logic levels to be set for the outputs are output when calling PCA6408_Write
*
*/
#define PCA6408_DEBUG 0