# Interfaces

The Interface Board for P1 is exactly the same as M2. It contains both the power supply circuitry and the automotive interfaces required to communicate with your car. This includes:

* 2x CAN bus
* 1x SWCAN (Single-Wire CAN)
* 2x LIN/9141
* J1850 VPW/PWM

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-Lhg646e0zcy2Yk5d5Sb%2F-Lhg6CD8Cb9DXtcE91wG%2FInterface_0d024.png?generation=1560886965355850\&alt=media)

## 26-pin **general purpose** connector

Every P1 has a 26-pin general purpose "expansion" connector that provides even more connection options. For example: UART, SPI, I2C, six general purpose 12V drivers and six 12V analog inputs. See the [schematic](https://github.com/macchina/P1-hardware) for actual pinout details.

Part number for this 2mm pitch connector is: [Hirose DF11-26DP-2DS(52)](https://www.digikey.com/product-detail/en/hirose-electric-co-ltd/DF11-26DP-2DS-52/H2876-ND/524308)

Refer to the following diagram for pin 1 location. Note that the **ODD** pins are on the **TOP** row and the **EVEN** pins are on the **BOTTOM** row.

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-Lhg646e0zcy2Yk5d5Sb%2F-Lhg6CDAodvSXcXpROkA%2F26pin_connector.png?generation=1560886964533811\&alt=media)

The following table shows what the function for each pin:

| Pin | Function         | Notes                   |
| --- | ---------------- | ----------------------- |
| 1   | IN 1             | 0-12V Analog Input      |
| 2   | OUT 1            | 12V SOURCE Output       |
| 3   | SCL0             | 3.3V logic              |
| 4   | SDA0             | 3.3V logic              |
| 5   | IN 2             | 0-12V Analog Input      |
| 6   | OUT 2            | 12V SOURCE Output       |
| 7   | UART3 TX         | 3.3V logic              |
| 8   | UART3 RX         | 3.3V logic              |
| 9   | IN 3             | 0-12V Analog Input      |
| 10  | OUT 3            | 12V SOURCE Output       |
| 11  | SPI0 CLK         | 3.3V logic              |
| 12  | SPI0 MISO        | 3.3V logic              |
| 13  | IN 4             | 0-12V Analog Input      |
| 14  | OUT 4            | 12V SINK Output         |
| 15  | SPI0 CS/USART2RX | 3.3V logic              |
| 16  | SPIO MOSI        | 3.3V logic              |
| 17  | IN 5             | 0-12V Analog Input      |
| 18  | OUT 5            | 12V SINK Output         |
| 19  | +12VIO           | +12V (switched output)  |
| 20  | +5V              | +5 (constant output)    |
| 21  | IN 6             | 0-12V Analog Input      |
| 22  | OUT 6            | 12V SINK Output         |
| 23  | +3.3V            | +3.3V (constant output) |
| 24  | +12V             | +12V (constant output)  |
| 25  | GND              | Ground                  |
| 26  | GND              | Ground                  |

## CAN

[Controller Area Network](https://en.wikipedia.org/wiki/CAN_bus)

CAN bus is a vehicle bus standard used in most cars built after 2006. It is a message-based protocol that allows modules within a car to communicate with one another. While the physical layer is understood and open, the actual meaning of the messages sent over the bus are not. While some messages are legislated to be "standard", the majority of CAN messages in your typical car are not well documented.

The P1 has 2 CAN channels (in addition to the single-wire CAN channel) that can interface directly to the CAN bus network of your car. The P1 uses the 2 built-in CAN controllers found in the SAM3X and 2 external TJA1051 transceivers. Here is a typical example:

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-Lhg646e0zcy2Yk5d5Sb%2F-Lhg6CDILoDl7_u0_Xo2%2FCAN_schematic.png?generation=1560886963552362\&alt=media)

Here is the link to the datasheet: <http://www.nxp.com/docs/en/data-sheet/TJA1051.pdf>

CAN bus connections can be found on either the 16-pin OBD2 connector on the under-the-dash P1 or the 24-pin connector used by the under-the-hood P1.

## Single-wire CAN

The Macchina P1 provides single-wire CAN support using a MCP2515 CAN controller.

## LIN

[Local Interconnect Network](https://en.wikipedia.org/wiki/Local_Interconnect_Network) bus is an inexpensive, single wire, serial network protocol used in many modern cars. Typically, LIN would be used to control and monitor lower-priority devices such as seat positions, door locks, radio and illumination.

The P1 has 2 LIN channels that can interface directly to the LIN bus network of your car. Your P1 uses 2 external TJA1027 transceivers connected via UART to the processor.

Here is the link to the datasheet: <https://www.nxp.com/docs/en/data-sheet/TJA1027.pdf>

Note that the TJA1027 transceiver is used for both LIN and ISO9141 (K-LINE/L-LINE) for a total of 2 channels.

LIN bus connections can be found on either the 16-pin OBD2 connector on the under-the-dash P1 or the 24-pin connector used by the under-the-hood P1.

Use following Commands to init the LIN-Bus:

```
config-pin P2_22 hi # Enable LIN-Bus1
config-pin P2_28 hi # Enable LIN-Bus2
config-pin P2_19 hi # Enable Power for LIN
```

Use following Commands to see if the Lin-Busses are working:

```
cat /tty/ttyS4 # Lin1
cat /tty/ttyS0 # Lin2
```

Attention: To use the LIN2 Bus, you will need to solder bridges on the R06 and R07 which are not soldered on the Board. Refer here for Instructions: [https://github.com/macchina/p1-hardware/blob/master/PCB-01010 R1 COMPONENT LOCATOR CLOSE UP.PDF](https://github.com/macchina/p1-hardware/blob/master/PCB-01010%20R1%20COMPONENT%20LOCATOR%20CLOSE%20UP.PDF)

{% tabs %}
{% tab title="Plain Text" %}

```
Add in boot/uEnv.txt the console option to redirect output to ttyS2:
console=ttyO2,115200n8


```

{% endtab %}
{% endtabs %}

## K-line (aka ISO9141, KWP2000)

ISO9141/K-line is typically found in Chrysler, European, and Asian vehicles built before around 2005. This protocol is similar to RS-232 but at different voltage levels and on a single, bidirectional line.

Some cars require a secondary line (sometimes referred to as L-Line).

P1 has two K-line channels and uses the TJA1027 transceiver to interface the 12-volt single bidirectional line from the vehicle to a 3.3V UART connection. While this part is designed for LIN, it is also K-line compatible. Here is typical interface circuit showing a channel of ISO9141/LIN connected to the UART channel of the processor.

K-line connections can be found on either the 16-pin OBD2 connector on the under-the-dash P1 or the 24-pin connector used by the under-the-hood P1.

![](https://1875989339-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Lhg5aaQ-eiSLOcDoH85%2F-Lhg646e0zcy2Yk5d5Sb%2F-Lhg6CDKfpsgw-jI1vSH%2FISO9141_schematic.png?generation=1560886965124615\&alt=media)

Here is the link to the datasheet: <https://www.nxp.com/docs/en/data-sheet/TJA1027.pdf>

## J1850

P1 supports both J1850 PWM (Pulse-width-modulation) and VPW (Variable Pulse width).

{% hint style="danger" %}
J1850 information below is specific to M2 (Arduino) and needs updating
{% endhint %}

**J1850 PWM** is typically found in older Ford vehicles and operates at 41.6 kb/s. The bus is active when `J1850+_BUS` is pulled HIGH to 5V and `J1850-_BUS` is pulled LOW to 0V.

**J1850 VPW** is typically found in older GM vehicles and operates at 10.4 kb/s.

The voltage range for each protocol is different (0-7V for VPW and 0-5V for PWM). To change between the levels required for PWM and VPW variants of J1850, use this signal:

`J1850_PWM_VPW` (P1 board signal name "J1850\_PWM\_nVPW")

This signal is connected to physical pin 123 (PB8) of the SAM3X. Make this pin HIGH for PWM and LOW for VPW

The following code that will both turn on power to J1850 circuit AND set level for either PWM or VPW:

```cpp
void setup() {
  pinMode(PS_J1850_9141, OUTPUT);
  pinMode(J1850_PWM_VPW, OUTPUT);
  digitalWrite(PS_J1850_9141, HIGH);  // LOW  = no power at +12V_SW/+5V_SW
                                      // HIGH = power at +12V_SW/+5V_SW
  digitalWrite(J1850_PWM_VPW, HIGH);       // LOW  = ~7.9v (VPW)
                                      // HIGH = ~5.9V (PWM)
}
void loop() {
}
```

These signals originate from the vehicle:

`J1850+_BUS` connects to pin 2 on the OBD2 port and is used by **BOTH** J1850 PWM and VPW.

`J1850-_BUS` connects to pin 10 on the OBD2 port and is used by J1850 PWM

These signals connect to the processor as OUTPUTS:

`J1850P_TX` (P1 board signal name "J1850+\_TX") is an OUTPUT from the processor used for BOTH J1850 PWM and VPW. "J1850+\_TX" is connected to pin 45 or PC18. This corresponds to the **PWMH6** on peripheral B.

* *With J1850\_PWM\_VPW = HIGH (i.e. PWM mode):* When this signal goes HIGH , pin 2 of the OBD2 connector is 5.5V. When this pin is LOW, pin 2 of the OBD2 connector is 0V.
* *With J1850\_PWM\_VPW = LOW (i.e. VPW mode):* When this signal goes HIGH , pin 2 of the OBD2 connector is 7.5V. When this pin is LOW, pin 2 of the OBD2 connector is 0V.

`J1850N_TX` (P1 board signal name "J1850-\_TX") is an OUTPUT from the processor and is used for J1850 PWM. "J1850-\_TX" is connected to pin 7 or PC23. This corresponds to the **PWML6** on peripheral B.

* *With J1850\_PWM\_VPW = HIGH (i.e. PWM mode):* When this signal goes HIGH , pin 10 of the OBD2 connector is 0V. When this pin is LOW, pin 10 of the OBD2 connector is 5V.

PWMH6 and PWML6 functionality is described in section 38: Pulse Width Modulation (PWM) of the SAM3X [datasheet](http://www.atmel.com/Images/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf).

These signals connect to the processor as INPUTS:

`J1850_PWM_RX` is an INPUT to the processor. "J1850\_PWM\_RX" is connected to pin 3 or PC28. This corresponds to the **TIOA7** on peripheral B.

`J1850_VPW_RX` is an INPUT to the processor. "J1850\_VPW\_RX" is connected to pin 4 or PC26. This corresponds to the **TIOB6** on peripheral B.

TIOB6 and TIOA7 functionality is described in section 36: Timer Counter (TC) of the SAM3X [datasheet](http://www.atmel.com/Images/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf).