/* Number of bits in a PS2 data packet (Start + 8 bits + Odd parity + Stop) */ #define PS2DATASIZE 11 // bit locations are down-count zero justified #define PS2BIT_PARITY 1 #define PS2BIT_START 10 #define PS2BIT_LSB 9 #define PS2BIT_STOP 0 /* Special scan codes */ #define LSHIFT 0x12 /* Left-shift on PS2 keyboard */ #define RSHIFT 0x59 /* Right-shift on PS2 keyboard */ #define KEYRELEASE 0xF0 /* Preceeds key code when key released */ #define EXTENDED 0xE0 /* Used for numeric keypad & arrow keys */ #define CAPSLOCK 0x58 /* Caps Lock key code */ /* Static local variables */ static volatile _data unsigned char bc_char; /* Scan code created by ISR */ static volatile _data unsigned char bc_char_temp; /* Scan code created by ISR */ static volatile _data unsigned char bc_bit_count; /* Bit counter for ISR */ static _bit BC_CHAR_RCVD; /* Set when character has been received */ static _bit BC_SHIFT; /* Set when shift key active */ static _bit BC_KEY_RELEASE; /* Set when release code 0xF0 received */ static _bit BC_DATA_TEMP; /* Temporary storage of incoming data bit */ static _bit BC_PARITY; /* cumulative XOR of incoming bits until parity bit is reached, then 1|0 for good|bad parity */ static _bit reset_ch; // set if start,parity,stop bits are incorrect unsigned char getbcch (void) // (unsigned char pos) { register unsigned char rx_char; /* Initially assume that nothing has been received from scanner yet */ rx_char = 0; // while(rx_char != 'r' && pos < TEXT_BUF_LENGTH) // { if (BC_CHAR_RCVD) { /* A PS2 byte has been received: process it */ switch (bc_char) { case KEYRELEASE: /* Flag a key release event */ BC_KEY_RELEASE = TRUE; break; case EXTENDED: /* The "extended" code has no meaning here, so ignore it */ break; case LSHIFT: case RSHIFT: /* If the previous byte was a key release, then revert */ /* back to lower case. Otherwise, flag a shift event. */ if (BC_KEY_RELEASE) { BC_SHIFT = FALSE; BC_KEY_RELEASE = FALSE; } else { BC_SHIFT = TRUE; } break; default: /* Any other code with bit 7 set is ignored ! */ if (!(bc_char & 0x80)) { /* If this follows a key release event, just clear */ /* the key release flag */ if (BC_KEY_RELEASE) BC_KEY_RELEASE = FALSE; else { /* Otherwise get the ASCII character from the lookup table. */ /* NOTE: Illegal codes return NULL from the lookup process. */ if (BC_SHIFT) rx_char = scan2ascii_shifted[bc_char]; else rx_char = scan2ascii[bc_char]; /* if(rx_char) { // put_ch(0,pos,rx_char); text_buffer[pos++] = rx_char; msec_delay(2); // put_ch(1,pos,text_buffer[pos]); // pos++; */ // } } } break; } // if (text_buffer[pos-1] == 'r') // text_buffer[pos-1]=''; /* Reset the bit counter in preparation for the next PS2 byte */ bc_bit_count = PS2DATASIZE; BC_CHAR_RCVD = FALSE; BC_PARITY = FALSE; reset_ch = FALSE; EX1 = TRUE; /* Enable EX1 interrupts again */ PS2DAT = TRUE; PS2CLK = TRUE; /* Unlock the scanner so that it can get more */ } // } return (rx_char); } _interrupt(2) void ps2ck_interrupt (void) { /* Shift in the data bit from PS2DAT */ #pragma asm PS2DATA equ P3.4 mov c,PS2DATA mov _BC_DATA_TEMP,c #pragma endasm switch (--bc_bit_count) { case PS2BIT_START: /* ps2 start bit should be LOW * if its not reset PS2CLK to force a resend */ if (BC_DATA_TEMP) reset_ch = TRUE; break; case PS2BIT_PARITY: /* PS2 calls for odd parity, so inverse of bitwise XOR * that has been built up in BC_PARITY should be the same * as the parity bit */ if ( ~BC_PARITY != BC_DATA_TEMP ) reset_ch = TRUE; break; case PS2BIT_STOP: /* Lock the scanner so that it doesn't send anything else */ PS2CLK = 0; /* lastly check that the stop bit is high */ if (!BC_DATA_TEMP) { reset_ch = TRUE; } else { /* Save the byte received */ bc_char = bc_char_temp; /* Flag 'getbcch()' that there is a byte ready to be processed */ BC_CHAR_RCVD = TRUE; } return; default: /* Not a start or parity bit, so shift in the data bit */ /* the lsb of the data is assigned to parity, subseqeunt * bits are xor'd. later the inverse of BC_PARITY is * compared to the parity bit of the PS2 packet */ if (bc_bit_count == PS2BIT_LSB) BC_PARITY = BC_DATA_TEMP; else BC_PARITY ^= BC_DATA_TEMP; #pragma asm mov a,_bc_char_temp mov c,_BC_DATA_TEMP rrc a mov _bc_char_temp,a #pragma endasm break; } /* any data frame errors we reset the reception parameters */ if(reset_ch) { /* ensure PS2DAT is high else the bc may be thinking a host * command is coming */ PS2DAT = 1; PS2CLK = 0; // pull low for at least 100us bc_bit_count = PS2DATASIZE; bc_char_temp = 0; BC_CHAR_RCVD = FALSE; BC_SHIFT = FALSE; BC_DATA_TEMP = 0; reset_ch = FALSE; /* put line high again to force a resend */ PS2CLK = 1; // clear the false interrupt made by messing with PS2CLK IE1 = 0; } }