wii_i2c.c

//----------------------------------------------------------------------------- ----------------------------------------
// Biblio: [standing on the shoulders of giants]
//    https://bootlin.com/labs/doc/nunchuk.pdf
//    https://www.hackster.io/infusion/using-a-wii-nunchuk-with-arduino-597254#toc-i2c-protocol-9
//    https://web.archive.org/web/20220000000000*/https://www.hackster.io/infusion/using-a-wii-nunchuk-with-arduino-597254
//    https://github.com/madhephaestus/WiiChuck/blob/master/src/Accessory.cpp#L14
//    https://wiibrew.org/wiki/Wiimote/Extension_Controllers
//    https://www.best-microcontroller-projects.com/i2c-tutorial.html
//
// WiiMote Extension Controller:
//    Bus Address : 0x52
//    Register autoincrements after each (byte is) read
//       0x00..0x05 ( 6 bytes) ... [r] Controller Data
//       0x20..0x2F (16 bytes) ... [r] Calibration Data
//       0x30..0x3F (16 bytes) ... [r] (A copy of the) Calibration Data
//       0x40..0x4F (16 bytes) ... [w] Encryption key(s)
//       0xFA..0xFF ( 6 bytes) ... [r] Perhipheral ID

//----------------------------------------------------------------------------- ----------------------------------------
#include  <stdlib.h>
#include  <stdint.h>
#include  <stdbool.h>

#include  <furi.h>
#include  <furi_hal.h>
#include  <furi_hal_i2c.h>

#include  "i2c_workaround.h"  //! temporary workaround for a bug in furi i2c [see header]

#include  "wii_anal.h"
#include  "wii_i2c.h"
#include  "wii_ec.h"

#include  "bc_logging.h"

//----------------------------------------------------------------------------- ----------------------------------------
// Wii Extension Controller i2c Bus address
static const uint8_t  ec_i2cAddr   = 0x52;

// Initialise for UNencrypted comms
static const uint8_t  regInit1     = 0xF0;
static const uint8_t  regInit2     = 0xFB;
static const uint8_t  cmdInit1[]   = {regInit1, 0x55};
static const uint8_t  cmdInit2[]   = {regInit2, 0x00};

// Initialise for ENcrypted comms
static const uint8_t  regInitEnc   = 0x40;
static const uint8_t  cmdInitEnc[] = {regInitEnc, 0x00};

// Crypto key (PSK),      base register : {0x40..0x4F}[2][8]
static const uint8_t  regEnc       = 0x40;  // ENC_LEN

// Controller State data, base register : {0x00..0x05}[6]
static const uint8_t  regJoy       = 0x00;  // JOY_LEN

// Calibration data,      base register : {0x20..0x2F}[16]
static const uint8_t  regCal       = 0x20;  // CAL_LEN

// Controller ID,         base register : {0xFA..0xFF}[6]
static const uint8_t  regPid       = 0xFA;  // PID_LEN

//+============================================================================ ========================================
// Hexdump a buffer to the logfile
//
#if LOG_LEVEL >= 4 // INFO

static
void  dump (const uint8_t* buf,  const unsigned int len,  const char* id)
{
	// snprintf() would be useful!
	char   s[128] = {0};
	char*  p      = NULL;

	strcpy(s, id);
	p = s +strlen(s);
	*p++ = ':';
	*p++ = ' ';
	*p++ = '{';

	for (unsigned int i = 0;  i < len;  i++) {
		uint8_t  hi = (buf[i] &0xF0) >>4;
		uint8_t  lo = (buf[i] &0x0F);

		hi = hi + ((hi > 9) ? ('A' -10) : '0');
		lo = lo + ((lo > 9) ? ('A' -10) : '0');

		*p++ = (char)hi;
		*p++ = (char)lo;
		*p++ = ',';
	}
	*p   = '\0';
	*--p = '}';
	INFO(s);
}

#else
#	define dump(...)
#endif

//+============================================================================ ========================================
//
//! -W-A-R-N-I-N-G-  :  THIS ENCRYPTION CODE SHOULD NEVER BE REQUIRED ... AS SUCH, I'VE NEVER TESTED IT
//
static
void  decrypt (uint8_t* buf,  const uint8_t* encKey,  const uint8_t reg,  unsigned int len)
{
#if 1  // Use standard algorithm
	// decrypted_byte = (encrypted_byte XOR encKey[1][address%8]) + encKey[2][address%8]
	for (uint8_t* p = buf;  p < buf+len;  p++)
		*p = (*p ^ encKey[(reg +(p -buf)) %8]) + encKey[8 +((reg +(p -buf)) %8)];

#else  //! This is (I think) a shortcut for an all-zero key [not tested]
	(void)encKey;
	(void)reg;
	for (uint8_t* p = buf;  p < buf+len;  p++)
		*p = (*p ^ 0x17) + 0x17;
#endif
}

//+============================================================================ ========================================
// Read the Extension Controller state
// ...and decode it in to something sane
//
// Returns: {0:OK, >0:Error}
//
int  ecRead (wiiEC_t* pec)
{
	ENTER;
	int  rv = 0;  // assume success

	if (!pec->init) {
		WARN("%s : device not initialised", __func__);
		rv = 1;
		goto bail;
	}

	if (!furi_hal_i2c_is_device_ready(i2cBus,i2cAddr, i2cTimeout)) {
		INFO("%s : device disconnected", __func__);
		pec->init = false;
		rv = 2;
		goto bail;
	}

	if (!furi_hal_i2c_trxd(i2cBus,i2cAddr, &regJoy,1, pec->joy,JOY_LEN, i2cTimeout,i2cReadWait)) {
		ERROR("%s : trxd fail", __func__);
		rv = 3;
		goto bail;
	}

	if (pec->encrypt)  decrypt(pec->joy, pec->encKey, regJoy, JOY_LEN) ;

	// Decode the readings (according to Controller type)
	ecDecode(pec);

bail:
	LEAVE;
	return rv;
}

//+============================================================================ ========================================
// Initialise an Extension Controller
//
//! To disable encryption, pass a NULL encryption key  <-- this is currently ALWAYS the case
//
bool  ecInit (wiiEC_t* pec,  const uint8_t* encKey)
{
	ENTER;

	bool  rv = false;  // assume failure

#if 0  //! i2c workaround
	//! I think this is done during OS startup - long before the plugin starts
	furi_hal_i2c_init();
#endif

#if 0  //! i2c workaround
	// May become relevant when the i2c issues are resolved
	// Take control of the i2c bus [which returns void !?]
	// --> firmware/targets/f7/furi_hal/furi_hal_i2c.c
	furi_hal_i2c_acquire(i2cBus);
#endif

	pec->init = false;  // assume failure

	// === See if the device is alive ===
	if (!furi_hal_i2c_is_device_ready(i2cBus,i2cAddr, i2cTimeout)) {
		TRACE("%s : waiting for device", __func__);
		goto bail;
	}
	INFO("%s : device connected", __func__);

	// === Initialise the device ===
	pec->init = false;  // This goes true AFTER the (optional) controller-specific init code

	// === Start the Extension Controller ===
	if (encKey) {  //! start in encrypted mode

		//! todo - should this happen here, or AFTER we've got the ID ?

	} else {

		if ( !furi_hal_i2c_tx(i2cBus,i2cAddr, cmdInit1,sizeof(cmdInit1), i2cTimeout) ) {
			ERROR("%s : init fail (dec1)", __func__);
			goto bail;
		}
		TRACE("%s : init OK1", __func__);

		if ( !furi_hal_i2c_tx(i2cBus,i2cAddr, cmdInit2,sizeof(cmdInit2), i2cTimeout) ) {
			ERROR("%s : init fail (dec2)", __func__);
			goto bail;
		}
		TRACE("%s : init OK2", __func__);
	}

	// === Retrieve the Extension Controller ID ===
	if (!furi_hal_i2c_trx(i2cBus,i2cAddr, &regPid,1, pec->pid,PID_LEN, i2cTimeout)) {
		ERROR("%s : T(R)x fail (pid)", __func__);
		goto bail;
	}
	if (pec->encrypt)  decrypt(pec->joy, pec->encKey, regJoy, JOY_LEN);
	dump(pec->pid, PID_LEN, "pid");  // debug INFO

	// Find the StringID in the lookup table
	for (pec->pidx = PID_FIRST;  pec->pidx < PID_ERROR;  pec->pidx++)
		if (memcmp(pec->pid, ecId[pec->pidx].id, PID_LEN) == 0)  break ;
	if (pec->pidx == PID_ERROR)  pec->pidx = PID_UNKNOWN ;
	pec->sid = ecId[pec->pidx].name;
	INFO("sid: %s", pec->sid);

	// === (optionally) Enable encryption ===
	if (!encKey) {
		pec->encrypt = false;

	} else {  // Controller WILL encrypt ALL tranmissions
//! this encryption code fails - should it be done earlier?
//! as it is probably never of any use, I'm kinda loathed to spend time on it
//! https://github.com/madhephaestus/WiiChuck/blob/master/src/Accessory.cpp#L138
		uint8_t   encTx[1+ENC_LEN] = {0};
		uint8_t*  ep               = encTx;

		pec->encrypt = true;

		// ** Start the Controller in ENcrytped mode
		if ( !furi_hal_i2c_tx(i2cBus,i2cAddr, cmdInitEnc,sizeof(cmdInitEnc), i2cTimeout) ) {
			ERROR("%s : init fail (enc)", __func__);
			goto bail;
		}

		// Copy the (symmetric) encryption key to the controller state table
		if (pec->encKey != encKey)
			memcpy(pec->encKey, encKey, ENC_LEN);

		// Build the encryption key packet
		*ep++ = regEnc;
		memcpy(ep, pec->encKey, ENC_LEN);

		// ** Send encryption key (PSK)
		if ( !furi_hal_i2c_tx(i2cBus,i2cAddr, encTx,(1+ENC_LEN), i2cTimeout) ) {
			ERROR("%s : key fail", __func__);
			goto bail;
		}

		TRACE("%s : init OK (enc)", __func__);
	}

	// === Some devices [eg. Drawsome/uDraw] require additional init code ===
	if ( ecId[pec->init].init && (ecId[pec->init].init(pec) == false) )  goto bail ;
	pec->init = true;

	// === Read calibration data ===
	if (!furi_hal_i2c_trx(i2cBus,i2cAddr, &regCal,1, pec->calF,CAL_LEN, i2cTimeout)) {
		ERROR("%s : trx fail (cal)", __func__);
		goto bail;
	}
	if (pec->encrypt)  decrypt(pec->joy, pec->encKey, regJoy, JOY_LEN);
	dump(pec->calF, CAL_LEN, "cal");

	ecCalibrate(pec, CAL_RESET | CAL_FACTORY);  // Load factory default calibration

	// === Initialise decode buffers ===
	pec->decN = 0;  // read in to decode[1] (yes, N=0 -> read in to dec[1])
	switch (ecRead(pec)) {
		case 0:  // read OK
			memcpy(&pec->dec[0], &pec->dec[1], sizeof(pec->dec[0]));
			dump(pec->joy, JOY_LEN, "joy");
			break;

		default:  // bug: unknown
		case 1:   // bug: not initialised - should never happen
			ERROR("%s : read bug", __func__);
			break;

		case 2:  // device gone
		case 3:  // read fail
			// Logging done by ecRead()
			pec->init = false;
			goto bail;
	}

	rv = true;  // yay :)

bail:
#if 0 //! i2c workaround
	furi_hal_i2c_release(i2cBus);
#endif

	LEAVE;
	return rv;
}