Pedal Interceptor

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Revision as of 17:55, 4 September 2019 by BogGyver (talk | contribs) (Flashing the firmware for Tesla Pedal)

The Comma Pedal is used to provide acceleration and regen braking capability on Tesla cars running Openpilot that do not have iBooster installed.

The Comma Pedal is an accelerator pedal interceptor. It is a device that is inserted between a car's electronic accelerator pedal and the DU (Drive Unit). It detects the voltage from the accelerator pedal which represents the pedal's position. It then writes that same voltage back out to the DU as if the accelerator pedal had produced it. When Openpilot is engaged, Openpilot sends the virtual acceleration position through the Comma Pedal instead.

Without electric brakes (iBooster) the car only uses regenerative braking. This is not enough for suddent slowdowns. YOU MUST BE READY TO MANUALLY BRAKE AT ANY MOMENT.

The Comma Pedal is connected to the Giraffe on CAN3-EPAS usually using a Y adapter (that you have to make).

What it Does

The Comma Pedal has 4 main systems:

  1. 2 Analog to Digital Convertors
    • This is used to read the voltage from the car's accelerator pedal into the Comma Pedal's processor. The accelerator pedal produces an output Voltage between 0 and 5 Volts.
  2. 2 Digital to Analog Convertors
    • This is used to send voltage back to the car's DU as if the accelerator pedal had produced it.
  3. 1 CAN Bus
    • The CAN Bus is the car's communication network. The Comma Pedal communicates with Openpilot using the CAN Bus. It connects to the Tesla Giraffe on CAN3.
  4. 1 USB
    • This is used to program and monitor the Comma Pedal, itself.

When Openpilot is NOT engaged, the Comma Pedal reads the voltage from the accelerator pedal and just passes it along to the DU.

When Openpilot IS engaged with longitudinal control, the Comma Pedal gets accelerator commands from Openpilot and emulates a accelerator pedal to the DU.

The Comma Pedal is constantly sending the physical accelerator pedal's position to the CAN bus for Openpilot to read.

Obtaining a Comma Pedal

You cannot buy a pre-built comma pedal from Comma. Fortunately there are other people in the community manufacturing and selling them:

Since they're currently always sold out as soon as new ones get in stock, you could also build it yourself (not recommended) or have one fabricated through a service like Macrofab.

Wiring a Tesla Pedal

Tesla pedal wiring.png
Pedal pinout.png
Pedal connector.png
Pedal CAN connection.png
Pedal in box.png

In order to create your Tesla Pedal you need:

  • 1x Comma Pedal board
  • 1x set of WPT-929 connectors w/ or w/o wires
  • 1x JST2 male conenctor
  • 1x JST2 female connector (or you can buy this and cut it and you're done)
  • box to hold the board (I used this one from Amazon). You will need to cut some small openings on the sides (and in front of the RJ45) if you use this one.

Note: the two JST2s are needed only if you chose not to use an ethernet cable to conenct your Pedal to the Tesla Giraffe rev B.

Use the diagram to conenct the female WSP-929 pedal connector to the IN side of the pedal board and the male WSP-929 connector to the OUT side of the pedal connector.

To connect the CAN BUS from the Pedal to the Tesla Giraffe you can either use an Ethernet cable to connect the two RJ45 ports (if you have a Tesla Giraffe rev B) or you can use twised wire (preffered) to connect positions 3 and 6 of the fake-ethernet port of the pedal board to the two JST2 connectors (male and female). We need both because you will plug the female one in the Giraffe's EPAS connector and then the EPAS Harness into the male JSP2. Red should be CAN+ and black should be CAN- (that's the convention also used in the image showing the CAN wire soldered to pins 3 and 6 of the fake ethernet port on the pedal baord).

Flashing the firmware for Tesla Pedal

You have to use a Tesla specific firmware on the pedal in order to work for Tesla. 

The firmware in my repo for the Tesla Pedal is located in the Panda repository under the tesla_pedal branch. You can flash the pedal from your computer or from the EON (I did it from the EON). If you have a new board, it will automatically start in DFU mode. To know which mode you're in look at the LED: no light = DFU mode, slow blink = normal flash mode, fast blink = normal operations.

First, you need to get the code from the repo:

cd /data
mkdir panda
git clone
cd panda
git checkout tesla_pedal
cd board/pedal

For a normal flash, I usually use two USB to miniUSB cables. One you connect to the Panda and one to the Pedal. We use CAN message to put the pedal in DFU mode then we program it.

First, connet the USB from the Panda to the EON. We will kill the OP instance and then we will send the DFU command via CAN:

tmux kill-session -t comma
./ --recover

Now the LED should be off. quickly change the two usb cables so now your EON is connected to the Pedal (if you use the same cable make sure you CONSTANTLY hold the brake pedal pressed so car does no go in CAR OFF mode. Once your EON is connected to the pedal run the update command

make recover

Once done, let car go off, reconnect your Panda to EON, reboot EON and you should be good to go.

In case of emergency, you can enter the DFU mode by applying 5 volts to a special point on the board while conencting the board to USB (to power it up). That usually requires at least 2 people: one to keep the jumper for 5V in place and the other to connect the USB. Instructions on how to enter DFU mode were create by @jfrux. Once in DFU mode, go to the pedal directory and run "make recover"

Installing the Tesla Pedal

To install the pedal, there are two steps:

  1. connecting the board to the accelerator pedal
  2. conencting the board to the Tesla Giraffe

This video for a similar product shows you what you have to do in order to install the pedal interceptror between the accelerator pedal and the car existing connector. Take your time and watch the video first. The process is not complicated if you just follow it step by step.

Once that is complete, disconnect the EPAS cable from the Tesla Giraffe and connect the female JSP2 from your pedal to the Giraffe. Then connect the EPAS cable to the male JSP2 from your pedal.

Using the Tesla Pedal

Without electric brakes (iBooster) the car only uses regenerative braking. This is not enough for suddent slowdowns. YOU MUST BE READY TO MANUALLY BRAKE AT ANY MOMENT.

Out of the box, OP will use the Tesla CC (with stalk spamming) to control CC. This in our OP implementation is called Adaptive Cruise Control or ACC. CC on Tesla only works above 18 MPH (29 km/h).

If you turn off the Tesla CC by pressing on the CC stalk, OP will switch to Tesla Pedal (PDL) mode. This will also provide you with adaptive cruise control by sending the right commands to your Tesla Pedal. Tesla pedal works down to 1 MPH, but be careful, regen brakes stop working at 5 MPH (8 km/h).

Once you get used to it and you don't care about ACC anymore, you can modify the config file to always use pedal

force_pedal_over_cc = True

Guides for Building / Troubleshooting Your Comma Pedal

Comma Pedal: Updating the Firmware over CAN by @jfrux Use this guide to update your Comma Pedal for compatibility with Openpilot v0.5.10+

Comma Pedal: Building with MacroFab by @jfrux

Comma Pedal: Flashing the Firmware by @jfrux