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How To Mask The Serial 8Th Bit

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Hi all and DJ,

I'm trying to figure out the syntax to mask the 8th bit of a packet serial command from EZ-B to RobotClaw Motor Controller, any help would be appreciated if it's possible on the EZ-B.

On other MCU's that I have I use this format...

Serout P15, i19200, [128, 0, 127 (255 & 0x7F) ]

Serout - well that's the command for output from the serial port,

in EZ-b that would be SendSerial.

P15 - is the port ...EZ-B D0

i19200 - is the baud rate...EZ-B just 19200 or whatever baud i use..

The 128, 0, 127, (255 & 0x7F) is "address, command, address, (checksum & 0x7F)

the 0x7F is the Hex code to mask the 8th bit.

Sooooo...

EZ-B code...

SendSerial ( D0, 19200, 128, 0, 127, (255 & 0x7F )

but it won't accept the "(255 & 0x7F)"

clear as mud eh!

:)


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Synthiam
#1  

255 & 0x7f = 127

So you'd use


SendSerial ( D0, 19200, 128, 0, 127, 127)

Check the datasheet for the motor controller, as that doesn't look correct. The datasheet i gave a quick look at is here. And the syntax for Simple Serial is...


# Stop
SendSerial(d0, 19200, 0)

# Channel 1 reverse
SendSerial(d0, 19200, 1)

# Channel 1 stop
SendSerial(d0, 19200, 64)

# Channel 1 forward
SendSerial(d0, 19200, 127)

# Channel 2 reverse
SendSerial(d0, 19200, 128)

# Channel 2 stop
SendSerial(d0, 19200, 192)

# Channel 2 forward
SendSerial(d0, 19200, 255)

# Both Channels Forward
SendSerial(d0, 19200, 127, 255)

# Both Channels Reverse
SendSerial(d0, 19200, 1, 128)

# Turn Left
SendSerial(d0, 19200, 1, 255)

# Turn Right
SendSerial(d0, 19200, 127, 128)
#2  

Thanks for the reply DJ but....

Sorry the device i'm using is the RobotClaw dual 30 amp

The simple serial is ok, it's the packet serial code that I need to use for my bot.

The problem is that the 255 & 0x7F comes up as an error in EZ-B,

the 255 is the checksum for the "128, 0 127, " and the & 0x7F is mask for the 8th bit

PRO
Synthiam
#3  

255 & 0x7f is decimal 127

127 = (255 & 0x7f) = 127 = (255 & 0x7f) = 127:)

#4  

I agree the 0x7F = 127 but the line of code is

SendSerial ( D0, 19200, 128, 0, 127, (255 & 0x7F ))

It still wouldn't work if I sent it like this

SendSerial ( D0, 19200, 128, 0, 127, (255 & 127 ))

because EZ-B doesn't like the & symbol

when I try to save in the script config I get the error...

Syntax Error: (255 & 127 is not in a valid format.

PRO
Synthiam
#6   

SendSerial ( D0, 19200, 128, 0, 127, 127)

(255 & 0x7f) = 127

#7  

ok so what would the code look like for

SendSerial ( D0, 19200, 128, 3, 89, (220 & 0x7F ))

PRO
Synthiam
#8   

SendSerial ( D0, 19200, 128, 3, 89, 92)
  1. Load Windows Calculator
  2. select View and choose Programmer
  3. To enter 220 (which is decimal) select DEC from the radio buttons
  4. Enter 220
  5. Press AND
  6. To enter 0x7f (which is hex) select HEX from the radio buttons
  7. Enter 7f
  8. Press =
  9. The answer will be displayed in HEX because that is the last format you used. Simply press DEC to view it in decimal

Windows calculator is actually quite powerful - I use it often

Who ever documented that protocol did a terrible job. I can see performing a bitwise AND operation on a variable, but not a constant. By performing (220 & 0x7f) would use many unneeded cycles of operations within the processor; where simply entering the value would suffice.

:)

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