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@@ -104,50 +104,47 @@ uint8_t ibm4704_recv_response(void) |
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return rbuf_dequeue(); |
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} |
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uint8_t ibm4704_recv(void) |
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{ |
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if (rbuf_has_data()) { |
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return rbuf_dequeue(); |
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} else { |
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return -1; |
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} |
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} |
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/* |
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Keyboard to Host |
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---------------- |
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Data bits are LSB first and Parity is odd. Clock has around 60us high and 30us low part. |
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____ __ __ __ __ __ __ __ __ __ ________ |
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Clock \____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ |
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____ __ __ __ __ __ __ __ __ __ _______ |
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Clock \_____/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ \_/ |
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____ ____ ____ ____ ____ ____ ____ ____ ____ ____ |
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Data ____/ X____X____X____X____X____X____X____X____X____X________ |
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Start 0 1 2 3 4 5 6 7 P Stop |
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Start bit: can be long as 300-350us. |
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Inhibit: Pull Data line down to inhibit keyboard to send. |
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Timing: Host reads bit while Clock is hi. |
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Timing: Host reads bit while Clock is hi.(rising edge) |
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Stop bit: Keyboard pulls down Data line to lo after 9th clock. |
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*/ |
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uint8_t ibm4704_recv(void) |
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{ |
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if (rbuf_has_data()) { |
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return rbuf_dequeue(); |
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} else { |
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return -1; |
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} |
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} |
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ISR(IBM4704_INT_VECT) |
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{ |
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static enum { |
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INIT, START, BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, PARITY, |
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} state = INIT; |
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STOP, BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7, PARITY |
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} state = STOP; |
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// LSB first |
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static uint8_t data = 0; |
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// Odd parity |
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static uint8_t parity = false; |
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ibm4704_error = 0; |
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// return unless falling edge |
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if (clock_in()) { goto RETURN; } // why this occurs? |
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state++; |
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switch (state) { |
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case START: |
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switch (state++) { |
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case STOP: |
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// Data:Low |
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WAIT(data_hi, 10, state); |
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WAIT(data_lo, 10, state); |
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break; |
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case BIT0: |
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case BIT1: |
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@@ -182,7 +179,7 @@ ERROR: |
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while (ibm4704_send(0xFE)) _delay_ms(1); // resend |
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xprintf("R:%02X%02X\n", state, data); |
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DONE: |
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state = INIT; |
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state = STOP; |
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data = 0; |
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parity = false; |
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RETURN: |