Category: Linux

This is based on the Raspberry Pi implementation of the Toner chip reset:

https://gist.github.com/joeljacobs/c57550cdb4e68e3b86d6b89fb58f305d

I am using a Raspberry Pi Zero W so the chip is BCM2835 instead and I can use 100Kbps/400KBps instead of 9600 baud as in the original code

The electrical pins we need is clustered on to top left, Pins 1 (3.3V), 3 (I2C SDATA), 5 (I2C SCLK), 9 (Ground)

While looking for the pinouts (https://pinout.xyz/pinout/i2c), I discovered a useful tool called i2cdetect that allows me to find out the address of the chips which means I can write a program automatically figure out the right image to load to the chip without looking:

sudo apt-get install i2c-tools
sudo i2cdetect -y 1

Since I don’t have cheap pogo pins lying around, I took the 2.4mm pitch (the standard size used in PC, Arduino and Raspberry Pi) jumper block I have (so all pins are set at equal lengths to make simultaneous contact) and hope somehow there’s 4 pins that kind of align with the contact, and it did. See pictures here:

You might be worried about shorting into the next pin or hooking something up in reverse damaging the chips, but luckily the chips survived. My guess is that it’s a good design to put the Vcc next to Ground on one side instead of making it symmetric so the polarity can be reversed. When reversed, SCL is set to low (Ground), SDA is pulled up to Vcc while there is no power supply, so no damage is done. Brilliant! The worst case for my poorly aligned jumper block is that SDA and Vcc might touch each other, but it doesn’t matter because it’s a perfectly legal hookup (just not communicating)!

So no worries if you didn’t touch the pins right! The only case it might go wrong is if you intentionally flip the block and slide it by two pins (reversing Vcc and Ground). Other cases (you are likely going to run into) are pretty much data lines getting hooked high or low levels while power lines not getting any supplies.

I’ve designed the program that it’ll detect the chip if you hook it up right and immediately program the chip (takes only a second), so you don’t have to hold the jumper for too long to worry about unstable contacts.

#!/bin/bash

# This program detects rewrite the toner chips to "full" for a Ricoh SP C250SF/DN Printer using Raspberry PI (defaults to BCM2835 models such as Raspberry PI Zero)

# The chip data is in file named "black" "cyan" "magenta" and "yellow".
# The pad closest to the edge is GND (-> Pin 9), followed by VCC (-> Pin 1) , DATA (-> Pin 3), and Clock (-> Pin 5).

# Be sure i2c is enabled and installed (it's turned off by default) on Raspbian

# This line is disabled because it takes too long to unregister i2c_bcm2835 to start from a clean slate
# modprobe -r i2c_bcm2835

# This program needs sudo permissios as it involves direct access to hardware
if [[ $EUID -ne 0 ]]; then
  echo "Need root permissions as this code involves direct hardware access. Try sudo"
  exit 2
fi

# Sets the baud rate
modprobe i2c_bcm2835 baudrate=400000

# Create I2C address to color map
COLORS=( [50]="yellow" [51]="magenta" [52]="cyan" [53]="black" )
# Detect chip I2C address
I2C_address=$( sudo i2cdetect -y 1 | grep 50 | sed -e 's/50: //;s/-- //g' )
# Keep the 0x5* address lines since only 0x50~0x53 is valid. Strip the 50: header, discard all "--" entries, and you are left with the detected address
HEX_I2C_address="0x$I2C_address"

# LED flash function
target_device="/sys/class/leds/led0/brightness"
function turn_off {
  echo 0 > ${target_device}
}
function turn_on {
  echo 1 > ${target_device}
}
function toggle {
  # Reads 0 for OFF and 255 for ON
  readin=$(cat ${target_device})
  # Condition 255 to 1 to reduce platform dependency
  state=$[$readin>0]
  # Not equal to 1 is XOR (flip)
  flip=$[$state != 1]
  # Display output
  echo $flip > ${target_device}
}

function flash_once {
  period=${1:-0.5}

  toggle
  sleep $period

  toggle
  sleep $period
}

function flash {
  times=${1:-1}
  period=$2
  for((i=1; i<=times; i++)); do
    flash_once $period
  done
}

if [ -v COLORS[I2C_address] ]; then
  # Meat
  color=${COLORS[I2C_address]}
  echo "Detected toner chip for color: $color"

  echo "Short flashes before starting. Long flashes after done. Ctrl+C if you want to terminate get back to prompt earlier during long flashes."
  flash 5 0.1

   # "address" counter sync up with the hex code index in file
   printf "Writing"
   address=0;
   datafile="${BASH_SOURCE%/*}/${color}"
   for i in $(cat $datafile); do
     i2cset -y 1 ${HEX_I2C_address} $address $i;
     address=$(($address +1));
     printf .
     flash 1 0
   done
   echo "Done!"
  flash 10 0.5
else
  echo "Invalid I2C address for SP C250DN/SF toner chips. ${I2C_address}"
  exit 4
fi

Turns out Linux’s dot sourcing (bash calling) syntax is relative to your current folder, not the scripts’ folder. So if you have one script calling another in the same folder when you are not currently at the same folder as the script (e.g. startup automation), the relative paths will be wrong. So instead of ./ , you should use this prefix instead:

${BASH_SOURCE%/*}/

I chose to flash the board’s only LED light quickly before starting and blink slowly a few times after it’s done for visual clues. It’s entirely optional. Here’s the guts of the code without the fancy indicators:

#!/bin/bash

# Sets the baud rate
modprobe i2c_bcm2835 baudrate=400000

# Create I2C address to color map
COLORS=( [50]="yellow" [51]="magenta" [52]="cyan" [53]="black" )

# Detect chip I2C address
I2C_address=$( sudo i2cdetect -y 1 | grep 50 | sed -e 's/50: //;s/-- //g' )
HEX_I2C_address="0x$I2C_address"

if [ -v COLORS[I2C_address] ]; then
  # Meat
  color=${COLORS[I2C_address]}

  # "address" counter sync up with the hex code index in file
  address=0;
  for i in $(cat ${color}); do
    i2cset -y 1 ${HEX_I2C_address} $address $i;
    address=$(($address +1));
  done
else
  echo "Invalid I2C address for SP C250DN/SF toner chips: ${I2C_address}"
fi

Download the package. Run program_toner

Just in case if people are wondering. The L01 chip’s datasheet is here:

---

To make a dedicated Raspberry Pi Zero device to run this script (program_toner) repeatedly on boot, I made a script loop_program_toner that runs the same program as infinite loop. I added 5 seconds of slow flashes after a successful write. To prevent the program from retrying too fast (sucking up computing resources) when there’s nothing connected to it, I wait for 1 second between each retries.

#!/bin/bash

if [[ $EUID -ne 0 ]]; then
  echo "Needs root permissions. Try sudo"
  exit -2
fi

while :
do
  bash "${BASH_SOURCE%/*}/program_toner"
  if (($?));
  then
    sleep 1;
  fi
done

There are a few steps needs to auto make this automated:

1. Have a user account dedicate to autorun the program on boot. In the example here, we’ll use Raspberry Pi’s default admin account
2. Auto-logged on by running sudo raspi-config, select (1) System Option > (S5) Boot / Auto Login > (B2) Console Autologin
3. Bless the said account with password free sudo rights: Run sudo visudo and add this to the end (replace admin with something else if you chose a different username)

admin ALL=(ALL) NOPASSWD:ALL

4. Call loop_program_toner in ./profile (startup script). Can place this at the bottom if your package folder is ~/spc250dn :

sudo ./spc250dn/loop_program_toner

The path can start with . or ~ because you are starting with at home folder anyway.

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