M18 lead map

The cords already in the plug, drawn onto the pads. One red board is used. The other red board stays in the drawer.

Before the iron

The pack is about 18 to 21 volts. A strand from B+ to B- welds and can start a fire. Unplug the USB lead. Take the shoe off the pack. Solder on the bare boards.

The yellow jumper on the blue board stays on 3V3. The 5V pad is not used.

Gold is the only new lead that may touch B+. It runs from HV on the red board to the outer blade. It never lands on the FT232. The yellow wire already in the plug is TXD, not B+.

Hold J2 low before the shoe touches the pack. If J2 sits high while you plug in, the pack counts a dumb charge. Run the idle step in the public reader first, then seat the shoe, B- first.

Your parts

FT232 with a rainbow lead, two red level boards, two black connectors, and an M18 pack on a plastic sheet.
Whole kit. The long black shoe with four flat pins is the one that meets the pack. The square block with the round hole does not.
Blue FT232 board. The yellow jumper is on the 3V3 side. The pin header is on the right.
Blue FT232. Leave the yellow jumper on 3V3. Solder only the pads whose silk says TXD, RXD, GND, and VCC or VCCIO.
Two red logic level converter boards. One shows the HV and LV labels. The other shows the chips.
Use the board whose silk you can read: HV along the top, LV along the bottom, GND in the middle of each row. The second board is a spare.

The cords

These are the six wires already in the grey shell, top to bottom, plus one new gold wire.

Cord map. Red CTS and black RTS stay unused. Orange RXD goes to J1. Yellow TXD goes to LV1 and from HV1 to J2. Green GND goes to the bottom GND hole and B-. Blue VCCIO goes to LV. A new gold wire goes from HV to B+.
Cord in the plugSilk on the blue boardSolder it to
Red, top wire CTS Nowhere. Leave it in the shell.
Black RTS Nowhere. Leave it in the shell.
Orange RXD Pack blade J1. This cord does not touch the red board.
Yellow TXD Red board LV1, the bottom-right hole. Continue yellow from HV1, the top-left hole, to pack blade J2.
Green GND Red board bottom GND, and on to pack blade B-.
Blue VCCIO Red board LV. The jumper is on 3V3, so this pad is 3.3 V.
Gold, new wire Not on the blue board Red board HV to pack blade B+. Nowhere on the FT232.

Leave empty: the 5V pad, HV2, HV3, HV4, the top GND, LV2, LV3, LV4, the second red board, and the square black block. If a pad says DTR, leave it open. Bridge DTR to TXD on the adapter only if the pack never answers. That bridge is for clone chips that cannot hold a break.

Which blade is which

The two outer blades are power. The two inner blades are the data pair. Do not trust left and right from a photo of a pack that can be turned around.

B+outer, gold
J1inner, orange
J2inner, yellow
B-outer, green
  1. Meter the two outer blades on DC volts. You should read about 18 V. The red meter probe is on B+.
  2. J1 is the inner blade touching B+. J2 is the inner blade touching B-.
  3. Put tape on the B+ end of the long black shoe before you solder, so it cannot be flipped later.
  4. The inner blades are not the 18 V pair. If the meter reads pack voltage on an inner blade, stop and look again.

Solder order

  1. USB unplugged. Shoe off the pack. Jumper still on 3V3. Red and black wires stay in the shell.
  2. Green from the plug GND pad to the red board’s bottom GND hole, then on to the shoe pin you marked B-.
  3. Blue from VCCIO to LV.
  4. Yellow from TXD to LV1. A second yellow from HV1, the top-left hole, to the shoe pin for J2.
  5. Orange from RXD straight to the shoe pin for J1.
  6. New gold wire from HV to the shoe pin you marked B+. Check that gold never touches a pad on the blue board.
  7. Look for a solder bridge between B+ and any other pin. Wick it before power.
  8. Plug USB. Run idle in the public reader so J2 is held low. Then seat the shoe, B- first.

Voltage check

Meter from B- to each data blade, after the shoe is seated.

J2, next to B-J1, next to B+
Idleunder 1 Vunder 1 V
Highover 8 Vover 2 V

A healthy pair on the published bench was about 0.13 V and 0.81 V at idle, and about 8.8 V and 3.3 V when high. If the red board gets hot, unplug. If J1 stays over 1 V at idle, this kit does not include the two-transistor isolator. Stop there.

The same four blades are on every M18 shell: CP, XC, High Output, HD, and Forge. Amp-hours change the cells inside the shell. They do not move these four contacts.

Source

The pad names follow the public wiring drawing and the device notes in discussion 16. The cord colors are the ones already in this plug. This page does not ship that software.

Wiring drawing and device list:

https://github.com/mnh-jansson/m18-protocol

https://github.com/mnh-jansson/m18-protocol/discussions/16