v1 Stable
Dependencies: F401RE-USBHost USBHostXpad mbed
main.cpp
- Committer:
- Ownasaurus
- Date:
- 2016-10-26
- Revision:
- 0:eb2258e8c4b5
- Child:
- 1:3c21da72660d
File content as of revision 0:eb2258e8c4b5:
#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; } } } }