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我正在使用 dsPIC33EV256GM002 开发一个项目，我想使用它的 UART。

所以我决定将 PIN18 用作 RX，将 PIN17 用作 TX，所以我将 PPS 编程如下：

// UART1 RX1 18 RP41 RPINR18 010 1001 (41)
// UART1 TX1 17 RP40 RPOR3.RP40R 000 0001 (1)
RPINR18bits.U1RXR=41;
RPOR3bits.RP40R = 1;

我将 PIN18 (RB 9) 作为输入设置 TRISB 的 bit9。

我使用了一个外部 8M XTAL，我将 M、N1 和 N2 参数设置如下：

// Configure Oscillator to operate the device at 80MHz/40MIPs
// Fosc= Fin*M/(N1*N2), Fcy=Fosc/2
// Fosc= 8M*40/(2*2)=80Mhz for 8M input clock
// To be safe, always load divisors before feedback


CLKDIVbits.PLLPOST = 0; // N1=2
CLKDIVbits.PLLPRE = 0; // N2=2
PLLFBD = 38; // M=(40-2), Fcyc = 40MHz for ECAN baud timer


// Disable Watch Dog Timer

RCONbits.SWDTEN = 0;

我想将 TX/RX 端口配置为 31250,N,8,1（标准 MIDI 参数）

// configure U1MODE
U1MODEbits.UARTEN = 0; // Bit15 TX, RX DISABLED, ENABLE at end of func
//U1MODEbits.notimplemented; // Bit14
U1MODEbits.USIDL = 0; // Bit13 Continue in Idle
U1MODEbits.IREN = 0; // Bit12 No IR translation
U1MODEbits.RTSMD = 0; // Bit11 Simplex Mode
//U1MODEbits.notimplemented; // Bit10
U1MODEbits.UEN = 0; // Bits8,9 TX,RX enabled, CTS,RTS not
U1MODEbits.WAKE = 0; // Bit7 No Wake up (since we don't sleep here)
U1MODEbits.LPBACK = 0; // Bit6 No Loop Back
U1MODEbits.ABAUD = 0; // Bit5 No Autobaud (would require sending '55')
U1MODEbits.URXINV = 0; // Bit4 IdleState = 1 (for dsPIC)
U1MODEbits.BRGH = 0; // Bit3 16 clocks per bit period
U1MODEbits.PDSEL = 0; // Bits1,2 8bit, No Parity
U1MODEbits.STSEL = 0; // Bit0 One Stop Bit



// U1BRG = (Fcy/(16*BaudRate))-1
// Fcy=40
// U1BRG = (40000000/(16*BaudRate))-1
// U1BRG = (40000000/(16*31250))-1 = 79

U1BRG = 79; // 40Mhz osc, 31250 Baud

// Load all values in for U1STA SFR
U1STAbits.UTXISEL1 = 0; //Bit15 Int when Char is transferred (1/2 config!)
U1STAbits.UTXINV = 0; //Bit14 N/A, IRDA config
U1STAbits.UTXISEL0 = 0; //Bit13 Other half of Bit15
//U1STAbits.notimplemented = 0; //Bit12
U1STAbits.UTXBRK = 0; //Bit11 Disabled
U1STAbits.UTXEN = 0; //Bit10 TX pins controlled by periph
U1STAbits.UTXBF = 0; //Bit9 *Read Only Bit*
U1STAbits.TRMT = 0; //Bit8 *Read Only bit*
U1STAbits.URXISEL = 0; //Bits6,7 Int. on character recieved
U1STAbits.ADDEN = 0; //Bit5 Address Detect Disabled
U1STAbits.RIDLE = 0; //Bit4 *Read Only Bit*
U1STAbits.PERR = 0; //Bit3 *Read Only Bit*
U1STAbits.FERR = 0; //Bit2 *Read Only Bit*
U1STAbits.OERR = 0; //Bit1 *Read Only Bit*
U1STAbits.URXDA = 0; //Bit0 *Read Only Bit*

IPC2bits.U1RXIP = 1; // Mid Range Interrupt Priority level, no urgent reason
IPC3bits.U1TXIP = 1; // Mid Range Interrupt Priority level, no urgent reason

IFS0bits.U1TXIF = 0; // Clear the Transmit Interrupt Flag
IEC0bits.U1TXIE = 1; // Enable Transmit Interrupts
IFS0bits.U1RXIF = 0; // Clear the Recieve Interrupt Flag
IEC0bits.U1RXIE = 1; // Enable Recieve Interrupts

U1MODEbits.UARTEN = 1; // And turn the peripheral on

供您参考，这是 OSC 配置

     _FOSCSEL(FNOSC_PRIPLL);
 _FOSC(FCKSM_CSDCMD & OSCIOFNC_OFF & POSCMD_XT);
 // Startup directly into XT + PLL
 // OSC2 Pin Function: OSC2 is Clock Output
 // Primary Oscillator Mode: XT Crystal

 _FWDT(FWDTEN_OFF); // Watchdog Timer Enabled/disabled by user software
 _FICD(ICS_PGD1); // PGD3 for external PK3/ICD3/RealIce, use PGD2 for PKOB

  _FDEVOPT( PWMLOCK_OFF );
  _FOSCSEL(FNOSC_PRIPLL);
  _FOSC(FCKSM_CSDCMD & OSCIOFNC_OFF & POSCMD_XT);
  // Startup directly into XT + PLL
  // OSC2 Pin Function: OSC2 is Clock Output
  // Primary Oscillator Mode: XT Crystal

由于检测到帧错误，我无法检测到来自串行 RX 的数据，因此我会知道我使用的设置是否正确。

你有类似的经历吗？

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