Input: add joystick driver for Walkera WK-0701 RC transmitter

Walkera WK-0701 transmitter is supplied with a ready to fly Walkera

helicopters such as HM36, HM37, HM60. The walkera0701 module enables to use

this transmitter as joystick

Devel homepage and download:

http://zub.fei.tuke.sk/walkera-wk0701/

or use cogito:

cg-clone http://zub.fei.tuke.sk/GIT/walkera0701-joystick

Connecting to PC:

At back side of transmitter S-video connector can be found. Modulation

pulses from processor to HF part can be found at pin 2 of this connector,

pin 3 is GND. Between pin 3 and CPU 5k6 resistor can be found. To get

modulation pulses to PC, signal pulses must be amplified.

Cable: (walkera TX to parport)

Walkera WK-0701 TX S-VIDEO connector:

 (back side of TX)

     __   __              S-video:                                  canon25

    /  |_|  \             pin 2 (signal)              NPN           parport

   / O 4 3 O \            pin 3 (GND)        LED        ________________  10 ACK

  ( O 2   1 O )                                         | C

   \   ___   /      2 ________________________|\|_____|/

    | [___] |                                 |/|   B |\

     -------        3 __________________________________|________________ 25 GND

                                                          E

I use green LED and BC109 NPN transistor.

Software:

Build kernel with walkera0701 module. Module walkera0701 need exclusive

access to parport, modules like lp must be unloaded before loading

walkera0701 module, check dmesg for error messages. Connect TX to PC by

cable and run jstest /dev/input/js0 to see values from TX. If no value can

be changed by TX "joystick", check output from /proc/interrupts. Value for

(usually irq7) parport must increase if TX is on.

Technical details:

Driver use interrupt from parport ACK input bit to measure pulse length

using hrtimers.

Frame format:

Based on walkera WK-0701 PCM Format description by Shaul Eizikovich.

(downloaded from http://www.smartpropoplus.com/Docs/Walkera_Wk-0701_PCM.pdf)

Signal pulses:

                   (ANALOG)

    SYNC      BIN   OCT

  +---------+      +------+

  |         |      |      |

--+         +------+      +---

Frame:

 SYNC , BIN1, OCT1, BIN2, OCT2 ... BIN24, OCT24, BIN25, next frame SYNC ..

pulse length:

   Binary values:		Analog octal values:

   288 uS Binary 0		318 uS       000

   438 uS Binary 1		398 uS       001

				478 uS       010

				558 uS       011

				638 uS       100

  1306 uS SYNC			718 uS       101

				798 uS       110

				878 uS       111

24 bin+oct values + 1 bin value = 24*4+1 bits  = 97 bits

(Warning, pulses on ACK ar inverted by transistor, irq is rised up on sync

to bin change or octal value to bin change).

Binary data representations:

One binary and octal value can be grouped to nibble. 24 nibbles + one binary

values can be sampled between sync pulses.

Values for first four channels (analog joystick values) can be found in

first 10 nibbles. Analog value is represented by one sign bit and 9 bit

absolute binary value. (10 bits per channel). Next nibble is checksum for

first ten nibbles.

Next nibbles 12 .. 21 represents four channels (not all channels can be

directly controlled from TX). Binary representations ar the same as in first

four channels. In nibbles 22 and 23 is a special magic number. Nibble 24 is

checksum for nibbles 12..23.

After last octal value for nibble 24 and next sync pulse one additional

binary value can be sampled. This bit and magic number is not used in

software driver. Some details about this magic numbers can be found in

Walkera_Wk-0701_PCM.pdf.

Checksum calculation:

Summary of octal values in nibbles must be same as octal value in checksum

nibble (only first 3 bits are used). Binary value for checksum nibble is

calculated by sum of binary values in checked nibbles + sum of octal values

in checked nibbles divided by 8. Only bit 0 of this sum is used.

	  This option enables support for the LED which surrounds the Big X on

	  XBox 360 controller.

config JOYSTICK_WALKERA0701

	tristate "Walkera WK-0701 RC transmitter"

	depends on HIGH_RES_TIMERS && PARPORT

	help

	  Say Y or M here if you have a Walkera WK-0701 transmitter which is

	  supplied with a ready to fly Walkera helicopters such as HM36,

	  HM37, HM60 and want to use it via parport as a joystick. More

	  information is available: <file:Documentation/input/walkera0701.txt>

	  To compile this driver as a module, choose M here: the

	  module will be called walkera0701.

endif

obj-$(CONFIG_JOYSTICK_WARRIOR)		+= warrior.o

obj-$(CONFIG_JOYSTICK_XPAD)		+= xpad.o

obj-$(CONFIG_JOYSTICK_ZHENHUA)		+= zhenhua.o

obj-$(CONFIG_JOYSTICK_WALKERA0701)	+= walkera0701.o

/*

 *  Parallel port to Walkera WK-0701 TX joystick

 *

 *  Copyright (c) 2008 Peter Popovec

 *

 *  More about driver:  <file:Documentation/input/walkera0701.txt>

 */

/*

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 as published by

 * the Free Software Foundation.

*/

/* #define WK0701_DEBUG */

#define RESERVE 20000

#define SYNC_PULSE 1306000

#define BIN0_PULSE 288000

#define BIN1_PULSE 438000

#define ANALOG_MIN_PULSE 318000

#define ANALOG_MAX_PULSE 878000

#define ANALOG_DELTA 80000

#define BIN_SAMPLE ((BIN0_PULSE + BIN1_PULSE) / 2)

#define NO_SYNC 25

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/parport.h>

#include <linux/input.h>

#include <linux/hrtimer.h>

MODULE_AUTHOR("Peter Popovec <popovec@fei.tuke.sk>");

MODULE_DESCRIPTION("Walkera WK-0701 TX as joystick");

MODULE_LICENSE("GPL");

static unsigned int walkera0701_pp_no;

module_param_named(port, walkera0701_pp_no, int, 0);

MODULE_PARM_DESC(port,

		 "Parallel port adapter for Walkera WK-0701 TX (default is 0)");

/*

 * For now, only one device is supported, if somebody need more devices, code

 * can be expanded, one struct walkera_dev per device must be allocated and

 * set up by walkera0701_connect (release of device by walkera0701_disconnect)

 */

struct walkera_dev {

	unsigned char buf[25];

	u64 irq_time, irq_lasttime;

	int counter;

	int ack;

	struct input_dev *input_dev;

	struct hrtimer timer;

	struct parport *parport;

	struct pardevice *pardevice;

};

static struct walkera_dev w_dev;

static inline void walkera0701_parse_frame(struct walkera_dev *w)

{

	int i;

	int val1, val2, val3, val4, val5, val6, val7, val8;

	int crc1, crc2;

	for (crc1 = crc2 = i = 0; i < 10; i++) {

		crc1 += w->buf[i] & 7;

		crc2 += (w->buf[i] & 8) >> 3;

	}

	if ((w->buf[10] & 7) != (crc1 & 7))

		return;

	if (((w->buf[10] & 8) >> 3) != (((crc1 >> 3) + crc2) & 1))

		return;

	for (crc1 = crc2 = 0, i = 11; i < 23; i++) {

		crc1 += w->buf[i] & 7;

		crc2 += (w->buf[i] & 8) >> 3;

	}

	if ((w->buf[23] & 7) != (crc1 & 7))

		return;

	if (((w->buf[23] & 8) >> 3) != (((crc1 >> 3) + crc2) & 1))

		return;

	val1 = ((w->buf[0] & 7) * 256 + w->buf[1] * 16 + w->buf[2]) >> 2;

	val1 *= ((w->buf[0] >> 2) & 2) - 1;	/* sign */

	val2 = (w->buf[2] & 1) << 8 | (w->buf[3] << 4) | w->buf[4];

	val2 *= (w->buf[2] & 2) - 1;	/* sign */

	val3 = ((w->buf[5] & 7) * 256 + w->buf[6] * 16 + w->buf[7]) >> 2;

	val3 *= ((w->buf[5] >> 2) & 2) - 1;	/* sign */

	val4 = (w->buf[7] & 1) << 8 | (w->buf[8] << 4) | w->buf[9];

	val4 *= (w->buf[7] & 2) - 1;	/* sign */

	val5 = ((w->buf[11] & 7) * 256 + w->buf[12] * 16 + w->buf[13]) >> 2;

	val5 *= ((w->buf[11] >> 2) & 2) - 1;	/* sign */

	val6 = (w->buf[13] & 1) << 8 | (w->buf[14] << 4) | w->buf[15];

	val6 *= (w->buf[13] & 2) - 1;	/* sign */

	val7 = ((w->buf[16] & 7) * 256 + w->buf[17] * 16 + w->buf[18]) >> 2;

	val7 *= ((w->buf[16] >> 2) & 2) - 1;	/*sign */

	val8 = (w->buf[18] & 1) << 8 | (w->buf[19] << 4) | w->buf[20];

	val8 *= (w->buf[18] & 2) - 1;	/*sign */

#ifdef WK0701_DEBUG

	{

		int magic, magic_bit;

		magic = (w->buf[21] << 4) | w->buf[22];

		magic_bit = (w->buf[24] & 8) >> 3;

		printk(KERN_DEBUG

		       "walkera0701: %4d %4d %4d %4d  %4d %4d %4d %4d (magic %2x %d)\n",

		       val1, val2, val3, val4, val5, val6, val7, val8, magic,

		       magic_bit);

	}

#endif

	input_report_abs(w->input_dev, ABS_X, val2);

	input_report_abs(w->input_dev, ABS_Y, val1);

	input_report_abs(w->input_dev, ABS_Z, val6);

	input_report_abs(w->input_dev, ABS_THROTTLE, val3);

	input_report_abs(w->input_dev, ABS_RUDDER, val4);

	input_report_abs(w->input_dev, ABS_MISC, val7);

	input_report_key(w->input_dev, BTN_GEAR_DOWN, val5 > 0);

}

static inline int read_ack(struct pardevice *p)

{

	return parport_read_status(p->port) & 0x40;

}

/* falling edge, prepare to BIN value calculation */

static void walkera0701_irq_handler(void *handler_data)

{

	u64 pulse_time;

	struct walkera_dev *w = handler_data;

	w->irq_time = ktime_to_ns(ktime_get());

	pulse_time = w->irq_time - w->irq_lasttime;

	w->irq_lasttime = w->irq_time;

	/* cancel timer, if in handler or active do resync */

	if (unlikely(0 != hrtimer_try_to_cancel(&w->timer))) {

		w->counter = NO_SYNC;

		return;

	}

	if (w->counter < NO_SYNC) {

		if (w->ack) {

			pulse_time -= BIN1_PULSE;

			w->buf[w->counter] = 8;

		} else {

			pulse_time -= BIN0_PULSE;

			w->buf[w->counter] = 0;

		}

		if (w->counter == 24) {	/* full frame */

			walkera0701_parse_frame(w);

			w->counter = NO_SYNC;

			if (abs(pulse_time - SYNC_PULSE) < RESERVE)	/* new frame sync */

				w->counter = 0;

		} else {

			if ((pulse_time > (ANALOG_MIN_PULSE - RESERVE)

			     && (pulse_time < (ANALOG_MAX_PULSE + RESERVE)))) {

				pulse_time -= (ANALOG_MIN_PULSE - RESERVE);

				pulse_time = (u32) pulse_time / ANALOG_DELTA;	/* overtiping is safe, pulsetime < s32.. */

				w->buf[w->counter++] |= (pulse_time & 7);

			} else

				w->counter = NO_SYNC;

		}

	} else if (abs(pulse_time - SYNC_PULSE - BIN0_PULSE) <

				RESERVE + BIN1_PULSE - BIN0_PULSE)	/* frame sync .. */

		w->counter = 0;

	hrtimer_start(&w->timer, ktime_set(0, BIN_SAMPLE), HRTIMER_MODE_REL);

}

static enum hrtimer_restart timer_handler(struct hrtimer

					  *handle)

{

	struct walkera_dev *w;

	w = container_of(handle, struct walkera_dev, timer);

	w->ack = read_ack(w->pardevice);

	return HRTIMER_NORESTART;

}

static int walkera0701_open(struct input_dev *dev)

{

	struct walkera_dev *w = input_get_drvdata(dev);

	parport_enable_irq(w->parport);

	return 0;

}

static void walkera0701_close(struct input_dev *dev)

{

	struct walkera_dev *w = input_get_drvdata(dev);

	parport_disable_irq(w->parport);

}

static int walkera0701_connect(struct walkera_dev *w, int parport)

{

	int err = -ENODEV;

	w->parport = parport_find_number(parport);

	if (w->parport == NULL)

		return -ENODEV;

	if (w->parport->irq == -1) {

		printk(KERN_ERR "walkera0701: parport without interrupt\n");

		goto init_err;

	}

	err = -EBUSY;

	w->pardevice = parport_register_device(w->parport, "walkera0701",

				    NULL, NULL, walkera0701_irq_handler,

				    PARPORT_DEV_EXCL, w);

	if (!w->pardevice)

		goto init_err;

	if (parport_negotiate(w->pardevice->port, IEEE1284_MODE_COMPAT))

		goto init_err1;

	if (parport_claim(w->pardevice))

		goto init_err1;

	w->input_dev = input_allocate_device();

	if (!w->input_dev)

		goto init_err2;

	input_set_drvdata(w->input_dev, w);

	w->input_dev->name = "Walkera WK-0701 TX";

	w->input_dev->phys = w->parport->name;

	w->input_dev->id.bustype = BUS_PARPORT;

	/* TODO what id vendor/product/version ? */

	w->input_dev->id.vendor = 0x0001;

	w->input_dev->id.product = 0x0001;

	w->input_dev->id.version = 0x0100;

	w->input_dev->open = walkera0701_open;

	w->input_dev->close = walkera0701_close;

	w->input_dev->evbit[0] = BIT(EV_ABS) | BIT_MASK(EV_KEY);

	w->input_dev->keybit[BIT_WORD(BTN_GEAR_DOWN)] = BIT_MASK(BTN_GEAR_DOWN);

	input_set_abs_params(w->input_dev, ABS_X, -512, 512, 0, 0);

	input_set_abs_params(w->input_dev, ABS_Y, -512, 512, 0, 0);

	input_set_abs_params(w->input_dev, ABS_Z, -512, 512, 0, 0);

	input_set_abs_params(w->input_dev, ABS_THROTTLE, -512, 512, 0, 0);

	input_set_abs_params(w->input_dev, ABS_RUDDER, -512, 512, 0, 0);

	input_set_abs_params(w->input_dev, ABS_MISC, -512, 512, 0, 0);

	err = input_register_device(w->input_dev);

	if (err)

		goto init_err3;

	hrtimer_init(&w->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);

	w->timer.function = timer_handler;

	return 0;

 init_err3:

	input_free_device(w->input_dev);

 init_err2:

	parport_release(w->pardevice);

 init_err1:

	parport_unregister_device(w->pardevice);

 init_err:

	parport_put_port(w->parport);

	return err;

}

static void walkera0701_disconnect(struct walkera_dev *w)

{

	hrtimer_cancel(&w->timer);

	input_unregister_device(w->input_dev);

	parport_release(w->pardevice);

	parport_unregister_device(w->pardevice);

	parport_put_port(w->parport);

}

static int __init walkera0701_init(void)

{

	return walkera0701_connect(&w_dev, walkera0701_pp_no);

}

static void __exit walkera0701_exit(void)

{

	walkera0701_disconnect(&w_dev);

}

module_init(walkera0701_init);

module_exit(walkera0701_exit);