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#include <xc.h>
#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <usb.h>
#include <usb_device.h>
#include <usb_device_cdc.h>
#include "usb.h"
/***** Constants *****/
// Line coding
// See struct USB_CDC_LINE_CODING
enum {
DATA_RATE = 9600, // bps
CHAR_FORMAT = NUM_STOP_BITS_1,
PARITY_TYPE = PARITY_NONE,
DATA_BITS = 8,
};
/***** Types *****/
// A state is a function that executes the state's action and returns the next state.
typedef struct State {
struct State* (*next)(void);
} State;
// Input buffer
typedef struct {
uint8_t data[CDC_DATA_OUT_EP_SIZE];
uint8_t len, head;
} RxQueue;
/***** Function Declarations *****/
// States
static State *idleState(void);
static State *echoState(void);
static State *writeEepromState(void);
static State *readEepromState(void);
/***** Global Variables *****/
static uint8_t txBuf[CDC_DATA_IN_EP_SIZE];
static RxQueue rxBuf = {.len = 0u, .head = 0u};
/***** Function Definitions *****/
// Return the next Rx'd char, or '\0' if no data.
static char
getchar(void) {
if (rxBuf.len <= 0u) {
rxBuf.len = getsUSBUSART(rxBuf.data, sizeof(rxBuf.data));
rxBuf.head = 0u;
}
if (rxBuf.len > 0u) {
rxBuf.len--;
return rxBuf.data[rxBuf.head++];
} else {
return '\0';
}
}
void
usbTask(void) {
static State state = {idleState};
USBDeviceTasks();
if (USBGetDeviceState() < CONFIGURED_STATE) {
return;
}
if (USBIsDeviceSuspended()) {
return;
}
if (USBUSARTIsTxTrfReady()) {
// Execute action and transition to next state
state = *state.next();
}
CDCTxService();
}
// Read (the start of) a command from USB.
static State *
idleState(void) {
static State state;
char opcode;
state.next = idleState;
// Read opcode
opcode = getchar();
if (!opcode) {
// No data
return &state;
}
// Skip space
if (!getchar()) {
// Incomplete command
putsUSBUSART("nack\n");
return &state;
}
// State transition
switch (opcode) {
case 'e': state.next = echoState; break;
case 'w': state.next = writeEepromState; break;
case 'r': state.next = readEepromState; break;
default: // invalid command
rxBuf.len = 0u; // discard input
putsUSBUSART("nack\n");
break;
}
return &state;
}
// Handle "e" echo command.
static State *
echoState(void) {
static State state;
uint8_t i;
state.next = echoState;
i = 0u;
while (i < sizeof(txBuf)) {
txBuf[i] = getchar();
if (txBuf[i++] == '\n') {
// End of command
state.next = idleState;
break;
}
}
if (i > 0u) {
putUSBUSART(txBuf, i);
}
return &state;
}
// Handle "w" write eeprom command.
static State *
writeEepromState(void) {
static State state;
// TODO
state.next = idleState;
return &state;
}
// Handle "r" read eeprom command.
static State *
readEepromState(void) {
static State state;
// TODO
state.next = idleState;
return &state;
}
static void
configure(void) {
line_coding.dwDTERate = DATA_RATE;
line_coding.bCharFormat = CHAR_FORMAT;
line_coding.bParityType = PARITY_TYPE;
line_coding.bDataBits = DATA_BITS;
}
bool
USER_USB_CALLBACK_EVENT_HANDLER(USB_EVENT event, void *pdata, uint16_t size) {
switch ((int)event) {
case EVENT_TRANSFER:
break;
case EVENT_SOF:
break;
case EVENT_SUSPEND:
break;
case EVENT_RESUME:
break;
case EVENT_CONFIGURED:
CDCInitEP();
configure();
break;
case EVENT_SET_DESCRIPTOR:
break;
case EVENT_EP0_REQUEST:
USBCheckCDCRequest();
break;
case EVENT_BUS_ERROR:
break;
case EVENT_TRANSFER_TERMINATED:
break;
default:
break;
}
return true;
}
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