first release for keyboard
Dependencies: F401RE-USBHost2 mbed
Diff: main.cpp
- Revision:
- 0:eb2258e8c4b5
- Child:
- 1:3c21da72660d
--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/main.cpp Wed Oct 26 02:02:09 2016 +0000 @@ -0,0 +1,159 @@ +#include "mbed.h" + +extern "C" void my_wait_us_asm (int n); + +DigitalOut myled(LED1); +Serial pc(USBTX, USBRX); // tx, rx +DigitalInOut data(PA_8); +DigitalIn button(PC_13); + +// 0 is 3 microseconds low followed by 1 microsecond high +// 1 is 1 microsecond low followed by 3 microseconds high +unsigned int GetMiddleOfPulse() +{ + // wait for line to go high + while(1) + { + if(data.read() == 1) break; + } + + // wait for line to go low + while(1) + { + if(data.read() == 0) break; + } + + // now we have the falling edge + // wait 2 microseconds to be in the middle of the pulse, and read. high --> 1. low --> 0. + my_wait_us_asm(2); + return (unsigned int) data.read(); +} + +// continuously read bits until at least 9 are read, confirm valid command, return without stop bit +unsigned int readCommand() +{ + unsigned int command = GetMiddleOfPulse(), bits_read = 1; + + while(1) // read at least 9 bits (2 bytes + stop bit) + { + //my_wait_us_asm(4); + command = command << 1; // make room for the new bit + //command += data.read(); // place the new bit into the command + command += GetMiddleOfPulse(); + command &= 0x1FF; // remove all except the last 9 bits + + bits_read++; + + if(bits_read >= 9) // only consider when at least a whole command's length has been read + { + if(command == 0x3 || command == 0x1 || command == 0x1FF) + { + // 0x3 = 0x1 + stop bit --> get controller state + // 0x1 = 0x0 + stop bit --> who are you? + // 0x1FF = 0xFF + stop bit --> reset signal + command = command >> 1; // get rid of the stop bit + return command; + } + } + } +} + +void write_1() +{ + data = 0; + my_wait_us_asm(1); + data = 1; + my_wait_us_asm(3); + //data = 0; + //pc.printf("1"); +} + +void write_0() +{ + data = 0; + my_wait_us_asm(3); + data = 1; + my_wait_us_asm(1); + //data = 0; + //pc.printf("0"); +} + + +void sendStop() +{ + data = 0; + my_wait_us_asm(1); + data = 1; +} + +void sendByte(unsigned char b) +{ + //pc.printf("\nTrying to send 0x%x\n",b); + for(int i = 0;i < 8;i++) // send all 8 bits, one at a time + //for(int i = 7;i >= 0;i--) // send all 8 bits, in reverse order, one at a time + { + if((b >> i) & 1) + { + write_1(); + } + else + { + write_0(); + } + } +} + +int main() +{ + __disable_irq(); // Disable Interrupts + pc.printf("SystemCoreClock = %d Hz\n", SystemCoreClock); + + while(1) + { + // Set pin mode to input + data.input(); + + // Read command + unsigned int cmd = readCommand(); + + //pc.printf("Read command: %u\n", cmd); + + my_wait_us_asm(2); // wait a small amount of time before replying + + // Set pin mode to output + data.output(); + + switch(cmd) + { + case 0x00: // identity + case 0xFF: // reset + //pc.printf("Received identity "); + // reply 0x05, 0x00, 0x02 + sendByte(0x05); + sendByte(0x00); + sendByte(0x02); + sendStop(); + break; + case 0x01: // poll for state + if(!button.read()) // simulate Start pressed + { + sendByte(0x08); // I think this is start, 4th bit + sendByte(0x00); + sendByte(0x00); + sendByte(0x00); + sendStop(); + break; + } + else + { + // respond with controller state + sendByte(0x00); + sendByte(0x00); + sendByte(0x00); + sendByte(0x00); + sendStop(); + break; + } + } + } +}