USB-Bluetooth Multiprotocol OBD II Adapter
on STN2120 OBD-UART Interpreter
with galvanic isolation.
Version 2.0
ATTENTION!!!
This project it is not commercial. All materials in this article are provided "as is". The author does not bear any responsibility for the use of his project for personal or commercial purposes. The exclusive right to copy and replicate the materials of the article has its author, as well as OBD Solutions LLC and Scantool.net LLC.
This article is devoted to replacing the STN1170 microcontroller in an already working adapter project with the STN2120 microcontroller. A description of the schematic diagram, design, additional materials and information can be found at the link:
USB-Bluetooth Multiprotocol OBD II Adapter
on OBD-UART Interpreter STN1170
with galvanic isolation.
In 2014, the adapter project for the STN1170 MCU was completed. This adapter has successfully worked for 6 years in various modes and has proven itself as a productive and trouble-free device.
But progress does not stand still. Company Scantool.net LLC released a new OBDII-UART interpreter
STN2120.
This is a 16-bit dspic33ep256gp504-I/ML microcontroller in a QFN-44 package from Microchip with firmware from the developer company Scantool.net LLC. Also, as in the previous article, I note that the STN2120 firmware is the intellectual property of the company Scantool.net LLC and does not exist " in nature " separately from the controller.
The characteristics of the microcontroller are as follows:
RAM - 32 KB (STN1170 - 8 KB)
Flash ROM - 256 KB (STN1170 - 128 KB)
Performance - 70 MIPS (STN1170 - 40 MIPS)
It is obvious that the STN2120 has a performance that exceeds the similar parameter of the STN1170 almost twice, which makes it very attractive for the design of modern diagnostic equipment.
So, it was decided to implement the adapter project on this microprocessor..
Before starting work on the project, it was necessary to have the STN2120 available, and therefore a request was sent to OBD Solutions to provide three copies of the MCU as part of the promotion. Microcontrollers were obtained and it was possible to start developing a circuit, printed circuit board, etc. At first, there was an idea to assemble the adapter in the OBDII connector housing, but after evaluating the dimensions of the final product, it was decided to abandon such an implementation. The fact is that in my version, this scheme simply will not fit in the above-mentioned case. Although it would be possible to try. But I decided not to strain myself and take as a basis an already working project by simply replacing STN1170 with STN2120. Moreover, they have full functional compatibility. The only difference is that some of the functional lines in the STN1170 and STN2120 are located on different pins. For safety reasons, a request was sent to the engineers of OBD Solutions for the interchangeability of STN1170 and STN2120 and as a result, a positive response was received.
Taking into account the differences between microcontrollers, the schematic diagram looks like this:
Changes in version 2.0 relative to version 1.1:
-STN1170 microcontroller replaced with STN2120.
-USB A connector replaced with micro USB B.
-Geyer KX-13 quartz resonator replaced with KX-9A.
-The nominal value of the load capacitors of the quartz resonator has been increased from 16 to 27 picofarads.
-Resistor R15 is replaced with a jumper.
-The value of the R40 resistor is reduced from 200 to 100 kilohms.
-For better cooling of the stabilizer +5V (VR2), a radiator is used
The printed circuit boards, as for the previous versions, were made on the basis of Plant of printed circuit boards "Electroconnect"
PCB`s v2.0.
Bluetooth module board assembly.
Adapter board assembly.
Adapter in case.
Interested and willing to get additional information, or to talk on this topic - welcome to Ford Focus Club, in the subject or a private messenger or e-mail scan11@yandex.com
Acknowledgements:
To people:
Bryan Lee. Engineer of company "OBD Solutions". Technical advice.
Firms:
"OBD Solutions". USA, Phoenix, Arizona state. MCU STN2120.
"Scantool.net LLC". USA, Phoenix, Arizona state. MCU STN2120.
"Electroconnect". Russia, Novosibirsk city. Printed Circuit Board factory.
May - August 2020 г.
Russia, Rostov-on-Don.
Scan Service Electronics Lab® by scan11
e-mail: scan11@yandex.com
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