AT91F_TWI_CfgPIO();
  AT91F_TWI_Configure(AT91C_BASE_TWI);
  *AT91C_TWI_CWGR = (F_MCK/F_TWI-6)/4 + ((F_MCK/F_TWI-6)/4 << 8) + (1<<16);   //=0x17676
  *AT91C_TWI_MMR = (2 << 8) | (TWIOp.dev->addr << 16);
  *AT91C_TWI_IADR = 0x57;

...
      //выдать start, адрес, данные
      while (len--) {
        *AT91C_TWI_THR = *buf++;
        *AT91C_TWI_CR = AT91C_TWI_START;
        do {
          tmp = *AT91C_TWI_SR;
          if (tmp & AT91C_TWI_NACK) {rprintf("NACK\r\n");break;}
          if (tmp & AT91C_TWI_OVRE) {rprintf("OVRE\r\n");break;}
          if (tmp & AT91C_TWI_UNRE) {rprintf("UNRE\r\n");break;}
        } while (!(tmp & AT91C_TWI_TXRDY));
        if (tmp & AT91C_TWI_NACK) break;
        if (tmp & AT91C_TWI_OVRE) break;
        if (tmp & AT91C_TWI_UNRE) break;
      }
      //выдать stop
      *AT91C_TWI_CR = AT91C_TWI_STOP;
      while (!(*AT91C_TWI_SR & AT91C_TWI_TXCOMP));