diff --git a/README.md b/README.md index 42170f9..7cb742e 100644 --- a/README.md +++ b/README.md @@ -96,6 +96,10 @@ Be aware Amazon links are Amazon Affiliate links. If you buy something through t - [comma four (C4)](#comma-four-c4) - [The Cable Not Plugged In All The Way Case (C4)](#the-cable-not-plugged-in-all-the-way-case-c4) - [The Can't Flash With comma's Cable Case (C4)](#the-cant-flash-with-commas-cable-case-c4) + - [comma chestnut](#comma-chestnut) + - [The Chestnut GPU Not Detected or USB Link Too Slow Case](#the-chestnut-gpu-not-detected-or-usb-link-too-slow-case) + - [The Chestnut Power Loss During Engine Start Case](#the-chestnut-power-loss-during-engine-start-case) + - [The GPS Signal Loss With Chestnut Case (C3X)](#the-gps-signal-loss-with-chestnut-case-c3x) - [See Also](#see-also) @@ -108,6 +112,7 @@ You must join the server with an invite linked for links to channels to work. * [comma.ai Discord (If unmarked and a link to Discord, it will be this)](https://discord.comma.ai/) * [#hw-three-3x](https://discord.com/channels/469524606043160576/871838269405556736) + * [#chestnut](https://discord.com/channels/469524606043160576/1185723603191337001) * [openpilot enthusiasts Discord (OPC), a degenerate community offshoot Discord](https://discord.gg/rRB7eDKccy) This document is generally discussed here and there in [#hw-three-3x](https://discord.com/channels/469524606043160576/871838269405556736). However, you're welcome to just make issues and discuss in the [GitHub issues](https://github.com/ophwug/docs/issues) of this repository too. @@ -1360,6 +1365,7 @@ There are multiple solutions to this problem. * Make sure the GPS module has power connections. * Heated windshields can cause issues with GPS reception. * It has not been explored, but there are GPS repeaters that can be used to help with this. Please report if you have success with this. +* If GPS reception worsens when chestnut is connected to a C3X, see [The GPS Signal Loss With Chestnut Case (C3X)](#the-gps-signal-loss-with-chestnut-case-c3x) for community cable and ferrite-choke reports. **Examples**: @@ -1969,6 +1975,128 @@ When tested with a simple USB-C cable tester, the missing `D+` and `D-` lines lo * [Erich's cable recommendation](https://discord.com/channels/469524606043160576/1436852432503046294/1534011423049383956) +## comma chestnut + +Released: 2026-08-12 + +https://blog.comma.ai/chestnut/ + +> [!NOTE] +> **Editor’s note:** I don’t own a chestnut or an officially compatible comma device. This section was generated by Codex from the linked sources. Own a chestnut and want to help? We’d welcome a human editor who can test the guidance and keep this section accurate. AI assistance is welcome! [Open an issue](https://github.com/ophwug/docs/issues) or submit a pull request with corrections, tested fixes, or an offer to help edit. + +chestnut is a desktop GPU compute upgrade for the comma four. Its USB-to-PCIe board connects the GPU to the comma so openpilot can run larger driving models. The [official shop and setup guide](https://comma.ai/shop/chestnut) describe two options: a dock for your own GPU and power supply, or a ready to drive kit. + +* The ready to drive kit includes an AMD Radeon RX 9060 8GB, a 3m USB3 cable, a vehicle power cable, and mounting strips, in addition to the dock and GPU assembly accessories. +* The GPU gets separate power from the vehicle's 12V accessory/cigarette-lighter socket. It also needs a USB data connection to the comma. +* Connect the GPU power cable to the dock before seating the GPU. Secure the GPU with the supplied standoffs and thumb nuts, then connect its 8-pin power lead. +* Secure the assembly in the passenger footwell or, if there is room, under the passenger seat. Leave airflow around the GPU and clearance for the seat to move. + +Use [the documented `release-chestnut` installer](https://installer.comma.ai/commaai/release-chestnut) for the official openpilot setup. The [openpilot README](https://github.com/commaai/openpilot/blob/ec95db3f1fa19f76940497fedfdb62e09ea19912/README.md#branches) lists the chestnut-specific release and development branches. + +The official in-car setup is for comma four. Older-device setups are community experiments: [geohot said that C3X was not really tested and had known GPS issues](https://discord.com/channels/469524606043160576/1185723603191337001/1537496880739647571). The C3X GPS case below documents those reports without establishing official compatibility. + +**Software note (checked 2026-10-03):** The [published `release-chestnut` 0.11.2 build](https://github.com/commaai/openpilot/blob/473eba53f280743d09c5bebc2d0613ea46883e02/openpilot/selfdrive/selfdrived/alerts_offroad.json) only has a chestnut-specific branch-selection alert. Detection, slow-USB, overheating, GPU/power, and model-error alerts are present in [newer development code](https://github.com/commaai/openpilot/blob/ec95db3f1fa19f76940497fedfdb62e09ea19912/openpilot/selfdrive/selfdrived/alerts_offroad.json). Both builds report version 0.11.2, so check the installed branch when comparing messages. For an overheating report, check airflow around the GPU as instructed by the setup guide. + +### The Chestnut GPU Not Detected or USB Link Too Slow Case + +**Symptoms**: + +* The chestnut-class model is unavailable even though the assembly is plugged in. +* On newer development builds, an alert reports missing chestnut hardware, a slow USB connection, or an unavailable GPU/PCIe link. +* A longer replacement USB cable gives unreliable connections. + +**Diagnosis**: + +USB detection and GPU availability are separate checks. The bridge can appear over USB while the GPU has no external power or working PCIe connection; see the power-loss example in [The Chestnut Power Loss During Engine Start Case](#the-chestnut-power-loss-during-engine-start-case). + +The [development diagnostics](https://github.com/commaai/openpilot/blob/ec95db3f1fa19f76940497fedfdb62e09ea19912/openpilot/system/hardware/chestnut/status.py) flag a negotiated USB speed below 5000 Mbps as slow and distinguish missing GPU power from a missing PCIe link. Normal model loading alone does not establish a hardware failure. + +**Resolution**: + +* With the car parked, start with the supplied USB3 cable and check the separate 12V power connection. Connect the data cable to chestnut's **USB3.2 port**, as shown in [comma's connection guide](https://github.com/commaai/comma_hack_7#run-on-chestnut). +* If you added a longer cable, extension, or hub, test a direct connection with the supplied cable first. A USB-C connector or advertised charging wattage does not establish that a cable can maintain the required data connection. +* If USB is detected but the PCIe link remains unavailable, disconnect power and USB before checking the GPU's seating, securing hardware, and power lead. Reassemble following the official setup guide. +* For bench testing, follow [comma's USB GPU check](https://github.com/commaai/comma_hack_7#run-on-chestnut), which expects `chestnut GPU check passed.` + +**Examples**: + +* [SirWilliam's C4 with a DIY RX 9060 XT 16GB setup](https://discord.com/channels/469524606043160576/1185723603191337001/1554850114135265472) + * Reported unreliable eGPU detection and [identified a 16.5ft replacement cable](https://discord.com/channels/469524606043160576/1185723603191337001/1554852897169346640). + * The discussion recommended testing the supplied cable first. A successful repair of this particular setup was not established in the cited messages. +* [demiller9's optical-cable report](https://discord.com/channels/469524606043160576/1185723603191337001/1555016941121310802) + * Reported that a phoossno optical USB-C cable had worked for several weeks. + * [Later clarified that the tested length was 7.5m](https://discord.com/channels/469524606043160576/1185723603191337001/1555338191073050796). Treat this as one tested configuration, rather than a guarantee for every optical cable or installation. + +**References**: + +* [inertiaimpact's advice to test the supplied cable before changing the cable setup](https://discord.com/channels/469524606043160576/1185723603191337001/1554886327076388875) +* [comma's chestnut connection guide and GPU checker](https://github.com/commaai/comma_hack_7#run-on-chestnut) +* [Development USB, GPU, and power diagnostics](https://github.com/commaai/openpilot/blob/ec95db3f1fa19f76940497fedfdb62e09ea19912/openpilot/system/hardware/chestnut/status.py) + +### The Chestnut Power Loss During Engine Start Case + +**Symptoms**: + +* The chestnut-class model fails while loading or running when the engine starts or an automatic start-stop system restarts it. +* The GPU is unavailable after starting from an engine-off, ignition-on state. +* USB may still detect the bridge, while the big model fails to load or the small model is used instead. + +**Diagnosis**: + +comma's [openpilot issue #38947](https://github.com/commaai/openpilot/issues/38947) documents engine-crank voltage drops that can brown out chestnut while the big model is active or loading. A vehicle outlet that supplies GPU power late is a related setup problem and can also leave the GPU unavailable when the model first tries to load. + +**Resolution**: + +* Park the car before troubleshooting. Check the 12V socket and chestnut power connection, and make sure GPU power is available before retrying. +* After restoring power, cycle ignition or restart the comma device. Users have reported needing the comma restart even after GPU power returned. Newer development diagnostics also direct users to cycle ignition after power loss or restoration. +* This is recovery guidance. It does not prevent the next engine-crank voltage drop. **As of 2026-10-03, issue #38947 remains open, and the proposed automatic retry in PR #38886 was closed without merging.** A retry proposal is not a shipped permanent fix. + +**Examples**: + +* [Adgower's C4](https://discord.com/channels/469524606043160576/1185723603191337001/1550162035877216299) + * Reported that engine start-stop interrupted chestnut operation and reconnecting the comma four restored it. + * For a stuck small-model state after power loss, reported restoring chestnut power before restarting the comma four. +* [Lincoln Navigator power/PCIe report in PR #38886](https://github.com/commaai/openpilot/pull/38886#issuecomment-5716592141) + * USB remained detected at 5000 Mbps while GPU power and PCIe were unavailable. + * Reconnecting restored GPU power, but restarting the comma four was still needed to load the big model. + +**References**: + +* [Engine-crank/start-stop brownout issue #38947](https://github.com/commaai/openpilot/issues/38947) +* [Closed, unmerged retry PR #38886](https://github.com/commaai/openpilot/pull/38886), including [the maintainer's decision to revisit it later](https://github.com/commaai/openpilot/pull/38886#issuecomment-5723044701) +* [Development power-loss and restoration guidance](https://github.com/commaai/openpilot/blob/ec95db3f1fa19f76940497fedfdb62e09ea19912/openpilot/system/hardware/chestnut/status.py) + +### The GPS Signal Loss With Chestnut Case (C3X) + +**Symptoms**: + +* GPS reception becomes poor or disappears when chestnut is connected to a C3X. +* Routes in [comma connect] have missing or noisy GPS positions. + +**Diagnosis**: + +This case concerns community C3X setups. [comma staff acknowledged C3X GPS issues and limited testing](https://discord.com/channels/469524606043160576/1185723603191337001/1537496880739647571). USB-related interference is a suspected contributor: users reported GPS improvement after changing the USB cable or adding ferrite chokes. These reports do not establish that every C3X setup will behave the same way. + +**Resolution**: + +* Compare GPS reception with chestnut connected and disconnected while parked to see whether its connection affects reception. +* Users have reported improvements from an optical USB cable or ferrite chokes on the USB cable near both the comma and chestnut. The specific outcomes and remaining limitations are below. +* Verify reception on your own setup and report the cable, GPU, software branch, and result. Improving GPS reception does not establish official support for the C3X configuration. + +**Examples**: + +* [inertiaimpact's C3X with a DIY RX 9060 XT 16GB setup](https://discord.com/channels/469524606043160576/1185723603191337001/1542756524798119997) + * Reported a route with no GPS points using the supplied cable, then a full GPS route after switching to [this specific 7.5m optical USB-C cable](https://www.amazon.com/dp/B0G1MC445S). + * This was a community GPU setup, rather than the ready to drive kit. +* [whoisdomi ('23 Ioniq 6 SEL)'s C3X](https://discord.com/channels/469524606043160576/1185723603191337001/1553017812488945795) + * Reported restored GPS reception with ferrite chokes near both ends of the cable. + * GPS lock still took longer than with chestnut disconnected. The user also tried copper tape but did not think it made much difference. + +**References**: + +* [geohot's C3X testing and GPS caveat](https://discord.com/channels/469524606043160576/1185723603191337001/1537496880739647571) +* [The Poor GPS Signal Case](#the-poor-gps-signal-case) for other causes of poor reception. + # See Also * https://docs.comma.ai/concepts/glossary/ - An official glossary of terms