The ELM327 Programmed Microcontroller

The ELM327 Programmed Microcontroller

What is the ELM327?

The ELM327 is a multi-protocol integrated circuit and PIC microcontroller that is used to translate the on-board diagnostics (OBD) interface for most modern automobiles. Produced by ELM Electronics, the ELM327’s command protocol is among the most popular PC-to-OBD interface standards on the market today.

Nearly every car being manufactured today is required by law to be equipped with an interface that allows for the connection of diagnostic test equipment. Although the data transfer on such interfaces normally follows a number of standards, none of these can be directly utilized by a PC or other smart device. The ELM327 therefore acts as the bridging connector between a standard RS232 serial interface and such OBD ports.

Apart from being capable of automatically detecting and interpreting up to 11 OBD protocols, the ELM327 also offers support for high-speed communications, a low-power sleep mode, as well as the J1939 truck and bus standards. If you wish to tailor the ELM327 so that it can more closely fit your needs, this programmed microcontroller is also fully customizable. Also applied by other vendors, the ELM327 is currently the most widely used integrated circuit for automobiles’ inside scan tools.

Some of the key functions and applications of ELM327 software include use in diagnostic trouble code readers, automotive scan tools, teaching aids, supplementary vehicle instrumentation, as well as reporting and clearing of error codes. You can learn more about the details of these functionalities on Total OBD & ECU Auto Diagnostics.

Background into the introduction and use of the ELM327

Elm Electronics has produced the ELM327 family of OBD translators since 2005. While the integrated circuit is today almost synonymous with the company, the earliest ELM327 was implemented on the PIC18F2480 microcontroller manufactured by Microchip Technology.

Since OBD was introduced early in the 1980s versions of on-board automobile computers, the amount of diagnostic information that is available using the system has been increasing steadily. While most of the original OBD versions would simply highlight a malfunction by illuminating its indicator or “idiot light” without providing further information about the nature of the problem detected on the vehicle, most modern OBD implementations provide real-time diagnostic data using a standardized digital communications port. Also implemented is a standardized series of diagnostic trouble codes (DTCs) that allow the owner of the car or the technician to easily identify any malfunctions within the affected car for quick remedy.

In 1968, Volkswagen of Germany was the first company to implement an on-board computer system with the capability to scan the inside of the company’s then-flagship fuel-injected Type 3 automobile models.

What protocols are compatible with the ELM327?

While most other variants of the ELM327 on the market today implement only part of the OBD protocols that the popular programmed microcontroller implements, there are 11 protocols that are currently supported by the ELM327. They include the following:

– SAE J1850 PWM (41.6 kbit/s);

– SAE J1850 VPW (10.4 kbit/s);

– ISO 9141-2 (5 baud init, 10.4 kbit/s);

– ISO 14230-4 KWP (5 baud init, 10.4 kbit/s);

– ISO 14230-4 KWP (fast init, 10.4 kbit/s);

– ISO 15765-4 CAN (11 bit ID, 500 kbit/s);

– ISO 15765-4 CAN (29 bit ID, 500 kbit/s);

– ISO 15765-4 CAN (11 bit ID, 250 kbit/s);

– ISO 15765-4 CAN (29 bit ID, 250 kbit/s);

– SAE J1939 (250kbps);

– SAE J1939 (500kbps);

Although majority of modern automobiles implement the ISO 15765-4 CAN protocol, yours may not use the same. You may need to seek professional advice from a vehicle repair technician if you need to know the protocol that your car implements. Check out this link { } for this information and more.

ELM327 applications

Apart from diagnosing car problems — which is the ELM327’s primary function — the integrated circuit is also used to reset faults as well as tap into the vehicle’s performance statistics. It allows for the performance of advanced diagnostics, health checkups as well as fault analysis on systems beyond the generic OBD II systems. Basically, the ELM327 is used to reach out and see everything that a person would want to know about the inside of their vehicle.

As highlighted earlier, the ELM327 is compatible with numerous programs and protocols, and is used to abstract the low-level protocols to present a simple application interface that can be called through a UART, typically via a handheld diagnostic tool or a computer program linked using a USB connection, RS-232, Wi-Fi or Bluetooth.

Today, new applications of the ELM327 also include smartphones.

Piracy Problems with the ELM327

The ELM327 is customized with the proprietary code from ELM Electronics that uses the testing protocols implemented in different vehicles it is used. When the mother company sold their first version of the ELM327, they never incorporated its copy protection feature. This resulted in a scenario where some unscrupulous business people could purchase a genuine ELM327 from the market, then put it into a device programmer and read its original proprietary binary microcontroller code.

Once they obtained this microcontroller code, they then could trivially produce their own ELM327 clones by buying the same microcontroller chips that Elm Electronics was purchasing from MicroChip and go on to program them with the copied microcode and sell to unsuspecting vehicle owners.

Such ELM327 clones were extensively circulated in fake devices that claimed to contain a genuine ELM327 device, with many problems being reported thereafter. Most of these problems reflect software bugs present in the microcode of the ELM327’s first version. Therefore, what customers continue getting are device clones that continue to sell the old bug-ridden version. Although most of the pirate clones on the market contain this version’s code, many falsely report their version numbers as the latest version that is provided by the genuine ELM327.

In some instances, some fake ELM327s even report a non-existent or yet-to-be-produced version of the proprietary software. The actual capabilities of these pirated versions is limited to the functionalities of the original ELM327 — with all its inherent bugs and deficiencies — yet some customers have bought it thinking it is the most recent version.

Elm Electronics avails the latest ELM327 in two voltage ranges: the ELM327 v2.1 (an IC that requires a Vdd supply of between 4.2V and 5.5V) and the ELM327L v2.1 (a PIC microcontroller integrated circuit that supports all the functions of the ELM327 v2.1 but which operates over a wider selection of supply voltages, typically between 2.0V and 5.5V).

The ELM327 Programmed Microcontroller
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