# CAN Stamp

<figure><img src="/files/8xPr1X4vhSyM34Qjykrk" alt="" width="375"><figcaption></figcaption></figure>

The stamp is based on the STM32L431 IC and contains a CAN Transceiver, Power Regulation and a 120 Ohm CAN termination resistor. Just give it 5v & CAN and you are away!

Features:

* STM32L431
* 17.8x18.9mm
* TJA1051
* 1 Amp 3.3v LDO
* Input Fuse and Diode
* 120 ohm Termination Resistor
* Fully compatible with Ardupilot and Px4 Firmware

## General Overview

The general stamp Architecture:

<figure><img src="/files/Dg0nVUn3FbyjXPI56OsF" alt=""><figcaption></figcaption></figure>

## Power Domain

<figure><img src="/files/PUtzWnujD651N7WR3d2j" alt=""><figcaption></figcaption></figure>

The stamp takes 5v in from the FC and regulates that down to 3.3v with an onboard 1 Amp LDO to power the L431.

Drone CAN specifies that all modules on the CAN Bus have their own input Diode and 1 Amp fuse. For ease of integration they are included on the stamp and are broken out to edge pads. This gives edge pads as follows:

* 5v In Pad (From FC)
* *Goes through fuse and diode*
* 5v Out Pad (Fused for any 5v sensors)
* *Fused 5v goes to 3v3 LDO internally and powers L431*
* Fused 3.3v Out Pad (Fused for any 3v3 sensors)

## CAN Interface

<figure><img src="/files/fil6nlIP217TmGKFm0Oo" alt=""><figcaption></figcaption></figure>

The CAN Interface goes between the L431 and the main bus and converts the logic from the L431 into differential signalling using a CAN transceiver.

The L431 is connected to the Transceiver using pins PB8 & PB9 and exits the stamp using Edge Pad 8&9.

CAN Bus stipulates the the device on each end of the bus should have a 120 ohm termination resistor between CAN High & CAN Low. The stamp contains this resistor but by default it is ***NOT*** connected. To connect it please connect Stamp Edge Pad 10 with CAN Low (Edge Pad 9) on your PCB.

## L431 Pinout and Useable Pins

<figure><img src="/files/D1bXIRH4H2xshhlXhjP7" alt=""><figcaption></figcaption></figure>

Some of the pins from the L431 are used on the stamp and are not broken out, these are:

* PB8 - CANRx
* PB9 - CANTx
* PB3 - LED

Others *are* broken out but are preferred to be unused (SWD Programming Pins, also connected to the pads on the bottom of the PCB)

* PA13 - SWDIO
* PA14 - SWDCLK

The rest are available for use (if they are supported by ardupilot):

* PC13
* PC13
* PC15
* PA0
* PA1
* PA2
* PA3
* PA4
* PA5
* PA6
* PA7
* PA8
* PA9
* PA10
* PA11
* PA12
* PA13 - SWDIO
* PA14 - SWDIO CLK
* PA15
* PB0
* PB1
* PB2
* ~~PB3 LED~~
* PB4
* PB5
* PB6
* PB7
* ~~PB8 CAN~~
* ~~PB9 CAN~~
* PB10
* PB11
* PB12
* PB13
* PB14
* PB15


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://wiki.cbunmanned.com/wiki/products/cbunmanned-stamp-eco-system/can-stamp.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.