MegaIO Peripheral Expander

7-bits

1-bit

1-byte

1-byte

1-byte

1-byte

1-byte

1-byte

Access Type

Serial port baud rate. Data format is a 32-bit number, written Low byte first, High byte last.
Example: 115200 baud = 0x0001C200 = [00 C2 01 00]

Serial port baud rate selector. This is an alternative way to select standard baudrate rates. Data format is an 8-bit number.
Possible values:
0x00 = 300 baud
0x01 = 600 baud
0x02 = 1200 baud
0x03 = 2400 baud
0x04 = 4800 baud
0x05 = 9600 baud
0x06 = 19200 baud
0x07 = 38400 baud
0x08 = 115200 baud

Number of bytes in the UART receive (RX) buffer. This is the number of bytes waiting to be read from the UARTDATA register. Data format is an 8-bit number.

Number of bytes in the UART transmit (TX) buffer. This is the number of bytes, written to the UARTDATA register, that are waiting to be transmitted out the serial port. Data format is an 8-bit number.

Control register for PWM1 outputs.
0x08 enables 8-bit PWM1 output
0x09 enables 9-bit PWM1 output
0x0A enables 10-bit PWM1 output
0x00 disables PWM1 output
Data format is an 8-bit number.

Control register for PWM1 output frequency.
0x00 = Freeze Outputs (zero frequency)
0x01 = Max Freq
0x02 = Max Freq/8
0x03 = Max Freq/64
0x04 = Max Freq/256
0x05 = Max Freq/1024
Data format is an 8-bit number.

PWM Channel 1A Duty Setting.
Data format is a 16-bit number, written Low byte first, High byte last.

PWM Channel 1B Duty Setting.
Data format is a 16-bit number, written Low byte first, High byte last.

A/D Converter Control Register
0x00 stops all A/D conversions
0x01 triggers a single A/D conversion
0x02 continuous A/D conversion
Data format is an 8-bit number.

A/D Converter Channel Select Register
Select an A/D input 0-7 by writing the channel number here. Data format is an 8-bit number.

A/D Conversion Result Register
Data format is a 16-bit number, Low byte first, High byte last.

PORTB
DDRB
PINB

PORTB Registers
These registers allow direct access to the processor I/O port. The registers operate as decribed in the Atmega8 datasheet.

PORTC
DDRC
PINC

PORTC Registers
These registers allow direct access to the processor I/O port. The registers operate as decribed in the Atmega8 datasheet.

PORTD
DDRD
PIND

PORTD Registers
These registers allow direct access to the processor I/O port. The registers operate as decribed in the Atmega8 datasheet.

DIRECTIO

Write/read directly to/from the processor's I/O space.
Access format: [ioaddr] [value*]
*To read, first issue an I2C write to DIRECTIO to set the ioaddr, but do not send a value. Then issue an I2C read from DIRECTIO to read the value at the previously-set IO address.

DIRECTMEM

Write/read directly to/from the processor's RAM memory space.
Access format: [memaddr_low] [memaddr_high] [value*]
*To read, first issue an I2C write to DIRECTMEM to set the memaddr, but do not send a value. Then issue an I2C read from DIRECTMEM to read the value at the previously-set memory address.

I2CADDR

Change MegaIO I2C address.
Access format: [0xB4] [0xC3] [new I2C address*]
* If the [new i2c address] field is omitted, then the address will be set back to the MegaIO default: 0x4C. New I2C address is stored in EEPROM and takes effect at next Power-On or RESET.

OSCCAL

Recalibrate the MegaIO internal oscillator.
Access format: [0xB4] [0xC3]
Sending 0xB4C3 to this register will trigger an oscillator calibration cycle. Before using this function, you must connect a 32.768KHz crystal to the XTAL1 and XTAL2 pins. Calibration takes approximately 20 seconds. The processor sends debug messages out the serial port at 115.2kbps during calibration.

// include AVRlib I2C functions
#include "i2c.h"

#define MEGAIO_I2C_ADDR		0x4C

// write one byte to a MegaIO register
void megaioWriteReg(unsigned char regnum, unsigned char data)
{
	u08 packet[2];

	// construct I2c data packet
	//   first byte is register address
	//   next byte is the data that will be written to that register
	packet[0] = regnum;
	packet[1] = data;
	// send 2 bytes (register and data) to MegaIO
	i2cMasterSend(MEGAIO_I2C_ADDR, 2, packet);
}

// read one byte from a MegaIO register
unsigned char megaioReadReg(unsigned char regnum)
{
	unsigned char data;

	// first select the register by writing 1 byte (register)
	i2cMasterSend(MEGAIO_I2C_ADDR, 1, ®num);
	// then read 1 byte from the selected MegaIO register
	i2cMasterReceive(MEGAIO_I2C_ADDR, 1, &data);
	// return the results
	return data;
}

void testUart(void)
{
	// set MegaIO baud rate to 9600
	megaioWriteReg(0x15, 0x05);
	// send "hello!" using the MegaIO uart
	megaioWriteReg(0x10, 'h');
	megaioWriteReg(0x10, 'e');
	megaioWriteReg(0x10, 'l');
	megaioWriteReg(0x10, 'l');
	megaioWriteReg(0x10, 'o');
	megaioWriteReg(0x10, '!');
}

void testPWM(void)
{
	// turn on PWM and set for 8-bit resolution
	megaioWriteReg(0x20, 0x08);
	// set PWM frequency for mid-range
	megaioWriteReg(0x21, 0x03);
	// set PWM1A for 50% duty = 256*50% = 128
	megaioWriteReg(0x24, 128);
	// set PWM1B for 25% duty = 256*25% = 64
	megaioWriteReg(0x25, 64);
}

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