Brother MFC-7820N network scanner protocol

Reasons

Brother MFC-7820N already has a scanner driver you can download here but that are prebuilt binary (x86/x64) and source code isn't public. This is a problem if you want to use the scanner on ARM architecture or FreeBSD, because if you don't have the source code of the driver you can't recompile it. Anyway this should work on every scanner that use brscan2, but I'm not sure.

Scanning protocol

Status codes

When we open a connection with the scanner on port 54921, it respond with his status code:

• +OK 200: Ready to use
• -NG 401: Scanner is busy

Lease

Now we can send a request that specify resolution and color mode, then scanner send to client a offer based on request. I called this part `lease because it recalled me DHCP lease

REQUEST

request := []byte(fmt.Sprintf("\x1bI\nR=%d,%d\nM=%s\n\x80", resolution, resolution, mode))
sendPacket(socket, request)

RESPONSE

300,300,2,209,2480,294,3472

• response[2] : ADF status

(X,Y)

• response[0] response[1]: Image DPI
• response[3] response[5]: Plane dimensions in mm
• response[4] response[6]: Image resolution in px

COLOR MODES

• GRAY64: gray scale image ** NOT IMPLEMENTED **
• CGRAY: color image ** NOT IMPLEMENTED **
• TEXT: low resolution mode, 1 bps

RESOLUTIONS

• 100x100
• 150x150
• 200x200
• 300x300
• 600x600
• 1200x1200 untested
• 1200x2400 untested

Start scan

Now we are ready to send start scan request:

width = mmToPixels(planeWidth, dpiX)
height = mmToPixels(planeHeight, dpiY)

requestFormat := "\x1bX\nR=%v,%v\nM=%s\nC=%s\nJ=MID\nB=50\nN=50\nA=0,0,%d,%d\n\x80"
request = []byte(fmt.Sprintf(requestFormat, dpiX, dpiY, mode, compression, width, height))

• R = X_DPI, Y_DPI
• M = CGRAY, GRAY64, TEXT
• C = JPEG or RLENGTH or NONE JPEG/RLENGTH UNTESTED
• D = SIN
• B = 50 (Brightness?)
• N = 50 (Contrast?)
• A = 0,0,WIDTH, HEIGHT

Compile

git clone https://github.com/corsmith/mfc-7820n.git
go build -o mfc-7820n mfc-7820n/src/*.go

Usage

./mfc-7820n --help

Output:

Usage of ./mfc-7820n:
  -a string
        IP address of the Brother scanner (default "192.168.0.157")
  -c string
        Color mode of the scan (CGRAY, GRAY64, TEXT) (default "TEXT")
  -m    Enable scan of all pages from feeder
  -n string
        Name of the output file (default "scan.tiff")
  -r int
        Resolution of the scan (default 300)
  -i string
	Name of the raw input file to parse instead of connecting to the printer

To do

• Implement CGRAY decoding
• Implement GRAY64 decoding

Credits

Corey Smith

Andrea Maugeri

Partially thanks to this