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ServoLX.cpp
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ServoLX.cpp
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/** \file
* LX-16A bus servo control library.
*
* Using the hardware serial port on the Teensy.
* Pinout:
*
* 10K
* TX -/\/\/---+
* |
* RX --------+-------
* 5V -----------------
* Gnd ----------------
*
*
* Motor angles are from 0-1000 covering 240 degrees == 0.24 deg/tick
* Read angles seem to match write angles
*/
#include "ServoLX.h"
#include <Arduino.h>
#include <stdint.h>
// Commands from the data sheet are in decimal, not hex
#define SERVOLX_ID_WRITE 13
#define SERVOLX_ID_READ 14
#define SERVOLX_POS_READ 28
#define SERVOLX_MOVE_TIME_WRITE 1
#define SERVOLX_MOVE_TIME_WAIT_WRITE 7
#define SERVOLX_MOVE_START 11
#define SERVOLX_MOVE_STOP 12
#define SERVOLX_MOTOR_MODE_WRITE 29
#define SERVOLX_LOAD_OR_UNLOAD_WRITE 31 // used to enable motor
void ServoLX::begin()
{
Serial1.begin(115200);
pinMode(tx_pin, INPUT_PULLUP);
}
void ServoLX::send_raw(const uint8_t * bytes, size_t len)
{
pinMode(tx_pin, OUTPUT);
pinMode(11, OUTPUT);
//digitalWrite(11, 1);
Serial1.write(bytes, len);
pinMode(tx_pin, INPUT_PULLUP);
digitalWrite(tx_pin, 1);
//digitalWrite(11, 0);
}
// look for a real packet
int ServoLX::recv_raw(uint32_t timeout_ms)
{
const uint32_t start = millis();
while(millis() - start < timeout_ms)
{
if (!Serial1.available())
continue;
int b = Serial1.read();
if (b == -1)
continue;
return (uint8_t) b;
}
return -1;
}
int ServoLX::recv()
{
// discard any previosly received data
while(Serial1.available())
Serial1.read();
//Serial1.clear();
uint8_t len = 255;
uint8_t offset = 0;
uint8_t checksum = 0;
digitalWrite(11, 1);
while(1)
{
const int rx = recv_raw(5);
if (rx < 0)
{
digitalWrite(11, 0);
Serial.println("timeout");
return -1;
}
const uint8_t b = rx;
if(0)
{
Serial.print(offset);
Serial.print(" ");
Serial.println(b, HEX);
}
// wait for a message start
if (offset == 0)
{
if (b == 0x55)
buf[offset++] = b;
continue;
}
if (offset == 1)
{
if (b == 0x55)
buf[offset++] = b;
else
offset = 0;
continue;
}
// inside the body, store the byte and checksum
buf[offset] = b;
checksum += b;
// if this is the length byte, record how many we should get
if (offset == 3)
{
len = b + 3;
//Serial.print("len="); Serial.println(len);
}
// if we have received the length byte, and we have all
// of the data, then we're done
if (++offset == len)
break;
}
digitalWrite(11, 0);
if (checksum != 0xFF)
{
Serial.print(checksum, HEX);
Serial.println(" checksum fail");
return -1;
}
//Serial.print(len);
//Serial.println(" bytes ok");
return len;
}
void ServoLX::send(uint8_t id, uint8_t cmd, const uint8_t * raw_bytes, size_t len)
{
uint8_t bytes[len + 6];
bytes[0] = 0x55;
bytes[1] = 0x55;
bytes[2] = id;
bytes[3] = len + 3; // length byte + data + checksum byte
bytes[4] = cmd;
uint8_t checksum = bytes[2] + bytes[3] + bytes[4];
for(size_t i = 0 ; i < len ; i++)
{
uint8_t c = raw_bytes[i];
bytes[5+i] = c;
checksum += c;
}
bytes[5 + len] = ~checksum;
send_raw(bytes, sizeof(bytes));
}
void ServoLX::enable(uint8_t which, uint8_t mode)
{
send(which, SERVOLX_LOAD_OR_UNLOAD_WRITE, &mode, 1);
}
int ServoLX::position_raw(uint8_t which)
{
send(which, SERVOLX_POS_READ);
while(1)
{
if (recv() < 0)
return SERVOLX_TIMEOUT;
if (msg->cmd != SERVOLX_POS_READ)
continue;
// ignore our query
if (msg->len == 3)
continue;
return (int16_t) (msg->buf[1] << 8) | msg->buf[0];
}
}
float ServoLX::position(uint8_t which)
{
int raw = position_raw(which);
if (raw == (int) SERVOLX_TIMEOUT)
return SERVOLX_TIMEOUT;
return raw * 0.24 - 120.0;
}
void ServoLX::move_raw(uint8_t which, uint16_t cmd_angle, int ms, bool wait)
{
uint8_t buf[] = {
(uint8_t)(cmd_angle >> 0),
(uint8_t)(cmd_angle >> 8),
(uint8_t)(ms >> 0),
(uint8_t)(ms >> 8),
};
send(
which,
wait ? SERVOLX_MOVE_TIME_WAIT_WRITE : SERVOLX_MOVE_TIME_WRITE,
buf,
sizeof(buf)
);
}
void ServoLX::move(uint8_t which, float angle, int ms, bool wait)
{
// keep it from slicing the cables
const float angle_limit = 90;
if (angle < -angle_limit)
angle = -angle_limit;
else
if (angle > +angle_limit)
angle = +angle_limit;
uint16_t cmd_angle = (uint16_t)((angle + 120) / 0.24);
move_raw(which, cmd_angle, ms, wait);
}
void ServoLX::start()
{
send(SERVOLX_BROADCAST, SERVOLX_MOVE_START);
}
void ServoLX::stop()
{
send(SERVOLX_BROADCAST, SERVOLX_MOVE_STOP);
}
int ServoLX::getid()
{
send(SERVOLX_BROADCAST, SERVOLX_ID_READ);
while(1)
{
if (recv() < 0)
return -1;
if (msg->cmd != SERVOLX_ID_READ)
continue;
if (msg->id == SERVOLX_BROADCAST)
continue;
return msg->buf[0];
}
}
void ServoLX::setid(uint8_t which)
{
send(SERVOLX_BROADCAST, SERVOLX_ID_WRITE, &which, 1);
}
typedef struct {
uint8_t mode;
uint8_t unused;
uint8_t speed_low;
uint8_t speed_hi;
} speed_msg_t;
void ServoLX::speed(uint8_t which, int16_t speed)
{
speed_msg_t msg = {
1, // motor mode
0,
(uint8_t)((speed >> 0) & 0xFF),
(uint8_t)((speed >> 8) & 0xFF),
};
send(which, SERVOLX_MOTOR_MODE_WRITE, (const uint8_t*) &msg, sizeof(msg));
}
void ServoLX::servo_mode(uint8_t which)
{
speed_msg_t msg = {
0, // servo mode
};
send(which, SERVOLX_MOTOR_MODE_WRITE, (const uint8_t*) &msg, sizeof(msg));
}