To build any electronic device, you have to understand intimately how it’s made. That’s why we’re publishing a series of posts that explore how popular consumer electronics are put together.
Automatic is a device that plugs into a port under the dashboard, designed to connect your car to the rest of your digital life by giving you access to its parameters such as speed and telematics.
Interaction with the car
To better understand what Automatic does and how it does it, let’s briefly review what cars look like on the inside.
Modern vehicles are complex systems containing a network of sensors and Electronic Control Units (ECUs). An ECU is a module responsible for a particular part of the vehicle. For example, an Engine Control Module, or ECM, takes care of timing the ignition and air/fuel ratio inside the engine, and a Telematic Control Unit, or TCM, tracks a car’s position via GPS and communicates via a central server over a cellular connection.
A basic unit of data on this network is a PID (Parameter Identification), which are key:value pairs allowing the car’s parameters to be read without the need to address each ECU for it’s data.
This network is accessible to the outside world via an ODB-II port (located under the dashboard near the steering wheel). The purpose of this port is two-fold: to diagnose potential problems and control emissions.
Although the physical dimensions of the port are standard across all cars, electrical protocols differ depending on car manufacturer. Automatic supports four of them:
— ISO 15765–4 CAN (US standard since ‘08)
— SAE J1850 PWM (Ford) / VPW (GM)
— ISO 9141–2 (European, Asian and Chrysler)
— ISO 14230–4 KWP2000 (European, Asian and Chrysler)
Automatic is not the first company to offer an interface to a car’s inner network. One of its main competitors is Kiwi, which offers a similar product. Kiwi’s app presents data on the dashboard, but does not offer anything beyond that.
Automatic differentiates itself by offering a more streamlined user experience and a whole ecosystem around the product.
Automatic works by making the information provided by a car’s inner sensors useful for drivers. It is useful for both businesses and individual drivers: for example, companies can track fuel usage and monitor car abuse in their fleet of vehicles and individual drivers can integrate their car data into their smart home, automize the repair process, or just stream the data to a dashboard.
The adapter is fairly small and designed to be hidden from view when inserted into the port.
After removing the grey skirt around the connector part and front cover, we get a first look at its insides.
The clever design simplifies the assembly process by allowing the PCB assembly to slip into the housing without solder or screws, where it sits under compression forces.
Looking closer at the PCB assembly, you can see additional grounding connections between two parts near the antenna connectors, probably to lower interference between them.
The PCB assembly is made of two 4-layered PCBs to minimize the volume of the device. The PCBs are held together with a screw on one side and data/power connector on the other. Exposed copper at the perimeter of both PCBs (Via fences) is there to decrease EMI (Electromagnetic Interference) with the outside world.
Let’s take a closer look at the PCBs themselves.
The top side of the top PCB features a dual mode (Bluetooth Classis + Bluetooth Low Energy) LBMA15Q1BX (or a variation) from Murata. The dual mode bluetooth chip ensures that the adapter will work with pretty much any smartphone (Low Energy became commonplace in 2012’s models for iOS and 2013’s for Android).
There’s also a GPS receiver G7020 from U-Blox. While the first version relied on GPS inside the phone, a dedicated GPS IC was added for the 2nd generation of the adapter to enable car tracking even when you’re not in it.
Both the GPS and Bluetooth antennas are integrated into a single custom flexible adhesive-backed part, which is stuck onto the front cover. This is done to both minimize the PCB size and increase antenna performance by removing it as far as possible from radiowave-blocking PCBs.
Also notice the holes in a hexagonal pattern on the front cover and matching exposed pads on the top PCB. These are used for updating the firmware and testing after the assembly is finished, but before the device has left the factory.
The bottom side has the low-power MCU STM32L151 from STM, 16MB of flash memory MX25L1606E from Macronix and an accelerometer LIS3DH from STM. The flash memory is used for temporary data storage before it is sent to the phone, and the accelerometer is used to detect emergency situations (such as collisions).
Note that both sides of this PCB are more-or-less uniformly colored — this is because their outside layers are ground. They are filled with copper to increase the performance of the wireless parts.
The top side of the bottom PCB has an STM’s Voltage Comparator LM239QT (used as a J1850, ISO 9141–2 and KWP2000 tranceiver) along with a pair of unidentifiable ICs in the center of the PCB (likely in receiver/transmitter configuration).
This side also has the circuitry to convert the +12V from car’s battery into +5V usable by the rest of the system, which is built on TI’s LP2951 voltage regulator.
While the division of PCBs was done to save space, there’s also a logical separation happening: the bottom PCB’s goal is to convert the myriad of electrical interfaces into an abstracted form, so that the top PCB doesn’t have to deal with it.
This is seen in the choice of MCUs for each part: a more powerful STM32F205 is used for the grunt work of doing the data transmission in several (potential) protocols and controlling the buzzer, while a simpler STM32L151 does the less-demanding work of merging the input data streams (GPS, accelerometer, PIDs) into Bluetooth (with buffering in on-board flash memory).
To sum up, the adapter is a well-designed system, from both the electrical and mechanical points of view. It is an example of a mass-manufactured product that combines small physical size with a lot of functionality.
Retail price: $99.95
Hope you enjoyed this teardown! Stay tuned for future posts about the construction of popular devices.
Text: Andrey Goverdosvky (embedded systems engineer, Lapka)
RUKI is a hardware incubator, based in Shenzhen, Moscow and San Francisco.
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