//******************************************************************************
//   MSP430xG461x Demo - 24xx EEPROM Emulation using USCI_B0 and DMA
//
//   Description: This code uses the USCI_B0 module in conjunction with
//   one DMA channel to emulate a 24xx-type EEPROM. It implements address
//   selection, current address read, random read, and sequential read
//   operations. The code is optimized for maximum efficiency to enable
//   zero-latency I2C communication in I2C fast mode as required by some
//   master devices such as the TUSB3410.
//
//   An application example, the EEPROM contents as used in the app note
//   SLAA276 is used and provided to the TUSB3410.
//
//   ACLK = 32kHz, MCLK = SMCLK = 8MHz
//
//                        /|\ /|\
//            TUSB3410    1k  1k      MSP430xG461x
//          ------------   |   |   -------------------
//         |         SDA|<-|---+->|P3.1/UCB0SDA    XIN|-
//         |            |  |      |                   | 32kHz
//         |            |  |      |               XOUT|-
//         |            |  |      |                   |
//         |         SCL|--+----->|P3.2/UCB0SCL       |
//         |            |         |                   |
//         |            |         |                   |
//         |            |         |               P1.4|--> SMCLK
//
//   Andreas Dannenberg
//   Texas Instruments Inc.
//   May 2006
//   Built with IAR Embedded Workbench Version: 3.41A
//******************************************************************************
#include "msp430xG46x.h"

#define EEPROM_ADDRESS       0x50           // Address for EEPROM emulation

//------------------------------------------------------------------------------
// The constant EEPROMImage[] contains the data to be loaded into the TUSB3410
// USB configuration EEPROM. It was generated using the tools provided in
// SLLC251 and then converted into a C constant. Note that the USB descriptor
// blocks contain checksums, therefore manual modification of the below EEPROM
// image is not recommended.
//
// USB vendor ID: 0x0451 (TI's VID)
// USB product ID: 0xbeef (This application's PID)
// USB product descriptor: "MSP430-TUSB3410 Reference Design"
//------------------------------------------------------------------------------
static const unsigned char EEPROMImage[] =
{
  0x10, 0x34, 0x03, 0x12, 0x00, 0x33, 0x12, 0x01,
  0x10, 0x01, 0xff, 0x00, 0x00, 0x08, 0x51, 0x04,
  0xef, 0xbe, 0x01, 0x01, 0x01, 0x02, 0x00, 0x01,
  0x05, 0x6c, 0x00, 0x34, 0x04, 0x03, 0x09, 0x04,
  0x24, 0x03, 0x54, 0x00, 0x65, 0x00, 0x78, 0x00,
  0x61, 0x00, 0x73, 0x00, 0x20, 0x00, 0x49, 0x00,
  0x6e, 0x00, 0x73, 0x00, 0x74, 0x00, 0x72, 0x00,
  0x75, 0x00, 0x6d, 0x00, 0x65, 0x00, 0x6e, 0x00,
  0x74, 0x00, 0x73, 0x00, 0x42, 0x03, 0x4d, 0x00,
  0x53, 0x00, 0x50, 0x00, 0x34, 0x00, 0x33, 0x00,
  0x30, 0x00, 0x2d, 0x00, 0x54, 0x00, 0x55, 0x00,
  0x53, 0x00, 0x42, 0x00, 0x33, 0x00, 0x34, 0x00,
  0x31, 0x00, 0x30, 0x00, 0x20, 0x00, 0x52, 0x00,
  0x65, 0x00, 0x66, 0x00, 0x65, 0x00, 0x72, 0x00,
  0x65, 0x00, 0x6e, 0x00, 0x63, 0x00, 0x65, 0x00,
  0x20, 0x00, 0x44, 0x00, 0x65, 0x00, 0x73, 0x00,
  0x69, 0x00, 0x67, 0x00, 0x6e, 0x00, 0x00, 0x00,
  0x00
};

// Function prototypes
void InitSystem(void);

// Implementation
void main(void)
{
  InitSystem();

  __enable_interrupt();
  __bis_SR_register(LPM0_bits);             // Enter LPM0
}

void InitSystem(void)
{
  WDTCTL = WDTPW + WDTHOLD;                 // Stop Watchdog timer

  // Clock system setup
  FLL_CTL0 |= DCOPLUS + XCAP18PF;           // DCO+ set, freq = xtal x D x N+1
  SCFI0 |= FN_4;                            // x2 DCO freq, 8MHz nominal DCO
  SCFQCTL = 121;                            // (121+1) x 32768 x 2 = 7.99 MHz
  P1SEL |= 0x10;                            // Output SMCLK on P1.4
  P1DIR |= 0x10;                            // Set P1.4 to output

  // Configure DMA Channel 0 to source the I2C Module
  DMACTL0 = DMA0TSEL_13;                    // Trigger is USCI_B0 transmit
  DMA0CTL = DMASRCINCR_3 + DMADSTBYTE + DMASRCBYTE;
  DMA0SA = (unsigned short)&EEPROMImage;    // Source is virtual EEPROM
  DMA0DA = (unsigned short)&UCB0TXBUF;      // Dest is USCI_B0 TX buffer
  DMA0SZ = sizeof EEPROMImage;
  DMA0CTL |= DMAEN;                         // Enable DMA channel 0

  // Init USCI_B0 Module for slave mode
  P3SEL |= 0x06;                            // Assign I2C pins to USCI_B0
  UCB0CTL1 |= UCSWRST;                      // Enable SW reset
  UCB0CTL0 = UCMODE_3 + UCSYNC;             // I2C Slave, synchronous mode
  UCB0I2COA = EEPROM_ADDRESS;               // Set Own Address
  UCB0CTL1 &= ~UCSWRST;                     // Clear SW reset, resume operation
  IE2 |= UCB0RXIE;                          // Enable RX interrupt
}

//------------------------------------------------------------------------------
// The USCIB0 data ISR is used to receive data from the TUSB3410 I2C master.
// This data is used as an EEPROM emulation start address by using the two
// received bytes as the start address for the next I2C read transaction. The
// DMA is used for efficient data transfers. Note that the temporary value
// 0xffff which is used to determine if the 1st/2nd byte was received is
// also generated CPU internal by the constant generator, thus allowing for
// a maximum-efficiency implementation.
//------------------------------------------------------------------------------
#pragma vector = USCIAB0TX_VECTOR
__interrupt void USCIAB0TX_ISR(void)
{
  static unsigned int EEPROMTemp = 0xffff;  // Assign initial value,
                                            // 'static' to preserve variable
                                            // over ISR calls

  if (EEPROMTemp == 0xffff)                 // MSB already received?
  {
    EEPROMTemp = UCB0RXBUF;                 // No, load address MSB
  }
  else                                      // Yes, re-assign DMA source addr
  {
    DMA0CTL &= ~DMAEN;                      // Disable DMA channel 0
    DMA0SA = (unsigned short)&EEPROMImage + (EEPROMTemp << 8) + UCB0RXBUF;
    DMA0CTL |= DMAEN;                       // Re-enable DMA channel 0
    EEPROMTemp = 0xffff;                    // Ready for new address
  }
}