Serial.write truncating output

Projects Programming
1

I have some Dynamixels and up to this point I have been using a laptop running PUREBASIC to experiment with them and defined over 30 command strings. I am now trying to duplicate the functions using an R4. Some like:

LEDOn:
Data.a $FF, $FF, $05, $04, $03, $19, $01, $D9

would be easy to program using the shield libraries, However some like:

Swish1:
Data.a $FF, $FF, $FE, $22, $83, $1E, $04, $02, $31, $04, $50, $00, $03, $0C, $06, $50, $00, $04, $0C, $06, $50, $00, $0A, $0C, $0A, $50, $00, $0B, $0C, $06, $50, $00, $0C, $0C, $06, $50, $00, $9D

would be very time consuming to decode and implement (I’m almost 70 and I don’t know if I would last that long).

The PUREBASIC program reads the array and writes the output to the serial port connected to the motors.

I tried to convert the LEDOn function but I couldn’t get it to work.

#include <DynamixelShield.h>

#define DEBUG_SERIAL Serial
// Dynamixel is Serial1

const uint8_t DXL_ID = 1;
const float DXL_PROTOCOL_VERSION = 1.0;

DynamixelShield dxl;

byte LEDOn[] = { 0xff, 0x80, 0x7f, 0x04, 0x03, 0x19, 0x01, 0xD9 };

int x;

using namespace ControlTableItem;

void setup() {

DEBUG_SERIAL.begin(9600);
dxl.begin(57600);
dxl.setPortProtocolVersion(DXL_PROTOCOL_VERSION);
}

void loop() {

DEBUG_SERIAL.println("LEDOn");

for (byte i = 0; i < 8; i = i + 1) {

DEBUG_SERIAL.print("print i = ");
DEBUG_SERIAL.println(i);

x = LEDOn[i];
DEBUG_SERIAL.print("print x = ");
DEBUG_SERIAL.println(x);

DEBUG_SERIAL.println(x, BIN);
 DEBUG_SERIAL.println();
DEBUG_SERIAL.println();

}

delay(5000000);
}

The issue, I think, is that the output of any value lower than 0x80 is truncated to significant digits. The LEDOn string in this example was modified to show this behavior. Here is the output:

print i = 0
print x = 255
11111111 <--- 8 bits

print i = 1
print x = 128
10000000 <--- 8 bits

print i = 2
print x = 127
1111111 <--- 7 bits

A couple of questions:

Is what I am seeing on line 3 of each output actually was is being written to the port?

If so is there a “reasonable” solution?

Thanks for any guidance.

2

Update to try to post sketch correctly.

#include <DynamixelShield.h>

#define DEBUG_SERIAL Serial
// Dynamixel is Serial1

const uint8_t DXL_ID = 1;
const float DXL_PROTOCOL_VERSION = 1.0;

DynamixelShield dxl;

byte LEDOn[] = { 0xff, 0x80, 0x7f, 0x04, 0x03, 0x19, 0x01, 0xD9 };

int x;

using namespace ControlTableItem;

void setup() {

DEBUG_SERIAL.begin(9600);
dxl.begin(57600);
dxl.setPortProtocolVersion(DXL_PROTOCOL_VERSION);
}

void loop() {

DEBUG_SERIAL.println("LEDOn");

for (byte i = 0; i < 8; i = i + 1) {

DEBUG_SERIAL.print("print i = ");
DEBUG_SERIAL.println(i);

x = LEDOn[i];
DEBUG_SERIAL.print("print x = ");
DEBUG_SERIAL.println(x);

DEBUG_SERIAL.println(x, BIN);
DEBUG_SERIAL.println();
DEBUG_SERIAL.println();

}

delay(5000000);
}
3

It is a known behavior that when printing a number via

DEBUG_SERIAL.println(x, BIN);

then all leading zeroes are not printed. Hence 1111111 is the expected output for the number 0x7f / 127.

The solution is to print all bits manually:

1 Like
4

I am not sure whether you are just testing the code logic at the moment, but there seem to be no statements actually sending bytes to the Dynamixel port as yet?

5

BitSeeker,

Thank you for the response. Yes, I had skinnied the sketch down to only what I thought would show me what was going on. In the full sketch I had:

Serial1.write(LEDOn[i]); within the loop. When it didn't work i stripped it out for testing.