我在通过 RS485 端口进行串行通信时遇到问题。
我正在使用带有 Max485 的 dsPic33E 微控制器。
使用断点我分析了每当我向控制器发送“0x00”时，都会收到“0xFF” 。然后我发送了“0x01”，控制器收到了“0xFD”，依此类推。
我也尝试使用环回逻辑，意味着发回接收到的字符，但每次我收到“0x00”发送的任何值。
我无法解决这个问题。下面是我正在使用的代码的快照：
// RS485
TRISBbits.TRISB6 = INPUT_PIN; // RX - RB6/RP38 PIN<42>
TRISBbits.TRISB7 = OUTPUT_PIN; // TX - RB7/RP39 PIN<43>
TRISBbits.TRISB8 = OUTPUT_PIN; // !RE/DE Control Pin RB8/RP40 PIN<44>
// RS485 Config
#define RS485_TX PORTBbits.RB6 // RS485 Transmitter
#define RS485_RX LATBbits.LATB7 // RS485 Reciever
#define RS485_CTRL LATBbits.LATB8 // RS485 Control Pin
void __attribute__((interrupt, no_auto_psv)) _U4RXInterrupt(void)
{
rs485Char = U4RXREG;
RS485_CTRL = 1; // Enable driver
U4TXREG = rs485Char;
RS485_CTRL = 0; // disable driver RE/DO
}
void InitClock( void )
{
PLLFBD = 63; // M=65
CLKDIVbits.PLLPOST = 0; // N2=2
CLKDIVbits.PLLPRE = 0; // N1=2
// Initiate Clock Switch to FRC oscillator with PLL (NOSC=0b001)
__builtin_write_OSCCONH(0x01);
__builtin_write_OSCCONL(OSCCON | 0x01);
// Wait for Clock switch to occur
while (OSCCONbits.COSC!= 0b001);
// Wait for PLL to lock
while (OSCCONbits.LOCK!= 1);
}
void InitRs485(void){
// configure U1MODE
U4MODEbits.UARTEN = 0; // Bit15 TX, RX DISABLED, ENABLE at end of func
U4MODEbits.URXINV = 1; // 1:URXINV Idle state is '0' ; 0=UxRX Idle state is '1';
U4MODEbits.ABAUD = 0; // Bit5 No Auto baud (would require sending '55')
U4MODEbits.BRGH = 0; // Bit3 16 clocks per bit period
U4MODEbits.PDSEL = 0; // 0 : 8 bit,no parity; 1 : 8 bit,even parity; 2 : 8 bit,odd parity; 3 : 9 bit,no Parity
U4MODEbits.STSEL = 1; // 1 : 2 Stop bits; 0 : 1 Stop bits
// Load a value into Baud Rate Generator.
U4BRG = BRGVAL_RS485; // 60Mhz osc, 9600 Baud
// Load all values in for U1STA SFR
U4STAbits.UTXISEL1 = 0; // Bit15 Int when Char is transferred (1/2 config!)
U4STAbits.UTXISEL0 = 0; // Bit13 Other half of Bit15
U4STAbits.UTXINV = 1; // 1:UxTX Idle state is '0' ; 0=UxTX Idle state is '1';
U4STAbits.UTXBRK = 0; // Bit11 Disabled
U4STAbits.UTXEN = 0; // Bit10 TX pins controlled by peripheral
U4STAbits.URXISEL = 0; // Bits6,7 Int. on character received
IPC22bits.U4RXIP = 7;
IPC22bits.U4TXIP = 7;
IFS5bits.U4TXIF = 0; // Clear the Transmit Interrupt Flag
IEC5bits.U4TXIE = 1; // Enable Transmit Interrupts
IFS5bits.U4RXIF = 0; // Clear the Receive Interrupt Flag
IEC5bits.U4RXIE = 1; // Enable Receive Interrupts
RPOR2bits.RP39R = 0x1D; // dsPic33EP512GM604 => RP39 as U4TX PIN<43>
_U4RXR = 38; // dsPic33EP512GM604 => RP38 as U4RX PIN<42>
U4MODEbits.UARTEN = 1; // And turn the peripheral on
U4STAbits.UTXEN = 1;
// Hardware control bits
RS485_CTRL = 0; // disable driver
IEC5bits.U4RXIE = 1;
}
int main(int argc, char** argv) {
InitClock(); // This is the PLL settings
InitPorts(); // Configure all Input/Output Ports
InitUarts(); // Initialize UART1 for 9600,8,N,1 TX/RX
Rs485Initialise( 0x10, 0x10);
while( 1 )
{
}
return (EXIT_SUCCESS);
}
这是一个测试代码。实际通讯将使用 Modbus 协议。请帮助我纠正问题。