I recently got a broken toy (Robot alpha 1s).
The main board is dead, but the 16 smart chainable servo motor are still good.
I am looking for a way to control them, but i haven't any documentation or datasheet (because it's a toy, and not an opensource one). The servo have no model number, but after some research, i have find them here : link
But the constructor didn't answer to my mails
have you any idea of how can i make them work ? (3 wire GND/Data/VIN and earch servo has an ID write on it).
Maybee somehow try to write / read on all the byte of the range in a big loop ?
May i use onewire to connect to it ? (already try but without succes).
Thanks ! (Sorry for any spelling mistakes, English is not my native language)
Thank's ! it's the same constructor, if i am lucky, the commands will be similar
But i still dont realy know how to send this hexa value to the motor from an adruino code.
I have try pluging the data pin of one servo on the arduino TX, and write hexa on the serial port like that :
void setup() {
 Serial.begin(115200);
}
void loop() {
 //Head
 Serial.write(0xFA);
 Serial.write(0xAF);
 //Data
 Serial.write(0x0B); // Servo ID 11
 Serial.write(0x01); // Go to
 Serial.write(0x01); // Value
 Serial.write(0x0A);
 Serial.write(0x00);
 Serial.write(0x01);
 //Check & End
 Serial.write(0x18);Â
 Serial.write(0xED);
Â
 delay(3000);
}
But it didn't work. (and strangely it write text on the serial monitor, whereas RX is not plug).
How can i send this hexa commande, is it possible with an arduino or have i to use some kind of 3 wire TTL board ?
The serial protocol for that is half duplex. Only one device ( servo or controller) can send data at a time.
You will have to manage 2 way communication over 1 line. You send a command and that command may require the servo to send data back to the controller all over just one wire.
The logic level for that servo may be 3.3V as mentioned at the end of that link.
You may want to put a 10K resistor inline on the data line for protection.
Without a controller sending data and reading the data(being able to sniff it) trying to figure out the protocol will be pretty hard to do.
It's the datasheet of the USB communication between a pc and the robot.
I know that this is not related to the servo protocol himself, but i have find out that it match perfectly with what the guy of your precedent link read (same hexa value at the same place).
That why i have good hope that it is the same, don't you think ?
It seems from the web page that while it is half duplex, you don't actually need to read the acknowledgements coming from the servos.
My question on the code (other than "why isn't it in [ code ] tags?") is How did you calculate the checksum? The servo could be rejecting the invalid checksum.
The USB-to-Serial converter is always plugged into Serial on the UNO, Mega and most other Arduinos. You can send data to a device on the serial pins 0 and 1 and the Serial monitor will also see it. Where you run into trouble is when the device is sending and you also send something on the Serial monitor. That will usually destroy any data sent during that time, from both sources. You also can't see the device's responses on the Serial monitor.
For this one, i have done it by hand :
0x0B + 0x01 + 0x01 + 0x0A + 0x00 + 0x01
= 11 + 1 + 1 + 10 + 0 + 1
= 24 => convert to hexa => 0x18
But i have make multiple attempt with different value, maybe my calculation are wrong ?
And i dont know if Serial.write() is the correct way for send hexa on the serial port ?
You mean that it is suppose to work, even with only the TX wire, as i try ?
What surprised me, is that i got text on the serial monitor with only TX link to the servo (RX link to nothing).
Yes, Serial.write(0xAA) is the correct way to write single bytes to the serial output.
I would not bother connecting to the Arduino RX unless you really need to see the servo's response. It may be useful during the debugging phase to use an Arduino with multiple hardware serial so you can send out on a dedicated port and also have a second port listening to what is said on that line.
Well, yes, you get Serial output on the Serial Monitor when you use Serial.write() and the Serial Monitor is connected. With a more advanced Arduino such as a Due or Teensy 3.x this won't happen. The USB serial is separate from the hardware serial. (Both of those are native 3.3V too.)
So maybee the only problem is that my arduino (Uno) TX is in 5v and the servo data is (maybee) in 3.3v.
I can have this 5v to 3.3v converter on monday : https://www.sparkfun.com/products/12009
I have already use it for i2c, but have no idea if it can do the job for serial at 115200 bps ?
Ok ! thank for the explanation, if i succeed to make them work, buy one of this board native in 3.3v would be a great idea
Yes, that level converter should work. 115200 is slower than default I2C frequencies. You will still need the pullup resistor on the low-voltage side like I2C.
#include <SoftwareSerial.h>
SoftwareSerial mySerial(10, 11); // RX, TX
void setup() {
 Serial.begin(9600);
 mySerial.begin(115200);
 Serial.println("start");
}
void srv(char id, char mode, char val){
 int sum = id + mode + val;
 char zero = 0;
 while(sum > 255){
  sum -= 255;
 }
Â
 //Head
 mySerial.write(0xFA);
 mySerial.write(0xAF);
 //Data
 mySerial.write(id);
 mySerial.write(mode);
 mySerial.write(val);
 mySerial.write(zero);
 mySerial.write(zero);
 mySerial.write(zero);
 //Check & End
 mySerial.write(sum);
 mySerial.write(0xED);
}
void srvFree(char id){
 srv(id, 2, 0);
}
void srvWrite(char id, char angle){
 srv(id, 1, angle);
}
void loop() {
Â
 srvWrite(2, 0);
 delay(100);
 srvFree(2);
 delay(2000);
Â
 srvWrite(2, 60);
 delay(100);
Â
}
