[bootloader architecture and brushing process based on UDS service]

be based on UDS Of BootLoader download , Can support ECU Infinite strokes of the life cycle , adopt CAN There is no need to dismantle the shell and DEBUG Application swiping of port , This paper introduces the brush writing service and the three-stage brush writing process . It can also be upgraded in the air through wireless modules , namely OTA technology .

See the following two pictures bootloader Software stack architecture and brushing process .

Questions

Q: The burning order in the figure is 34-36-34-36-34-36-37, But the order in other materials is 34-36-36-36-37.

A: This problem is understood in this way ,34-36-36-36-37 The premise is that the data you want to download is continuous data , Every 36 Address information used , All are 34 The address information contained in plus a certain offset . If you need to download discontinuous data , It needs to be repeated 34 Service or 31（ erase ）-34 service .

1 Why do we have to do Bootloader？ Why based on UDS To make Bootloader
If your controller has a shell , But there is no design bootloader Words , Each update ECU The program , You need to take the shell apart , Use the burner to update the program . With bootloader, You can go through CAN Line to update the program . If it's more convenient , Even through OTA Perform a remote upgrade .

Then why use UDS Well ？ It's mainly to standardize bootloader The whole process . For example, burning Xiaoming cards ECU when , We definitely want other brands ECU In a state of silence , Have a rest , This requires a common standard to be standardized , When to stop sending data , When can I no longer store DTC Wait a minute .

Another example is when debugging , You must want your controller to pass CAN The process of burning is understandable , Is satisfied with a certain specification . thus ,UDS In the design, we considered bootloader The needs of , Specially for bootloader Designed several services , For your use . When the main engine factory sends out the demand, it naturally requires everyone to UDS Complete on the basis of specifications bootloader The function of .

2 Bootloader What should be supported UDS service
obviously bootloader No support required 19/14 And other fault Services .

stay boot In the program ,10/27/11/3E Such basic diagnostic services need support ,22/2E Reading and writing DID Our services need support ,31/34/36/37 this 4 individual bootloader The main service needs support , common 10 individual .

stay app In segment program ,85 and 28 Service needs support , Make sure to pause CAN Normal communication , Pause recording DTC, Let the upgraded device concentrate on upgrading .

3 Bootloader—— Three paragraph
（1） Pre programming phase

3E TP message .
10 Service switch to 03 Extended mode .
85 Service and 28 service , Turn off DTC And non diagnostic messages . Make the whole CAN The network is quiet . This is to operate the whole vehicle network , Generally, it is sent in the way of functional addressing . Pay attention to use first 85 Service closing DTC, Reuse 28 Service close message .

（2） Main programming phase

10 The service switches to programming mode , Pay attention here , The right way is App Segment program reply 0x78 NRC, Next, jump to boot This program , Finally by Boot Segment program to reply 10 02 Positive response . The wrong way is by App Paragraph reply 10 02 Positive response , Then jump .
Read a DID,tester To judge the return value . The return value may contain some information of the key .
27 service , Unlock , Through security verification .

Be careful 10 02 The service should not directly respond positively , Risk exists

Write DID The fingerprint , Mark the identity of the person who wrote the software ,ECU Reply to write fingerprint successfully .（ according to OEM Request to execute ）
31 service - erase Flash.ECU Positive response , Erase succeeded .
34 service , Request data download ,ECU Reply to confirm the maximum block size .
36 service , Start transmitting data . After each block transmission is completed ,ECU Positive response . Determine if there are more blocks to download . Can support at most 255 Block .
37 service , Request to exit the transmission .ECU Positive response .
31 service - check APP This program , Check programming consistency / integrity .ECU Positive response . Check success .
If there are more blocks to download , Re execution 31（ erase Flash Area ）-34-36-37-31（ check ） service . If there is no , To perform the .
11 service ,ECU Reset . Then you should jump directly to the newly downloaded APP In segment program .

（3） Post programming status

10 Service switch to 03 Extended session .
perform 28 Service and 85 service , Enable non diagnostic messages and DTC. This is to operate the whole vehicle network , Generally, it is sent in the way of functional addressing . Pay attention to execute first 28, After execution 85, avoid DTC False positives .

27 service , Security check , Prepare to write data .
2E service , Write programming information to ECU in .
10 service , return 01 Default session . end .

4 BootLoader Start sequence and conversion process
The following process is for reference only , There are many irregularities . Welcome to leave a message to discuss .

ECU After power on or reset , Enter the first Boot paragraph . from Flash/EEPROM Read from App Valid marks , function boot sign .
Judge function boot sign , if 1, entering Boot Segment programming session （ The safety level is locked ）, Then write Flash/EEPROM（ Unsafe operation ）, function boot sign Zero clearing . if S3 If the timer times out, it will return Boot Segment default session .
Enter after security access Level2 Unlock state , Start execution App Memory erase , After erasing App Valid marks Zero clearing （ Unsafe operation ）.
Start burning . After burning successfully function boot sign Write 0,App Valid marks Write 1.
2*. Judge function boot sign , if 0, entering Boot Default session for segment .

3*. 50ms Post judgment App Valid marks , if 1, be Jump to App Segment default session . Assembly instructions are used to execute APP This program ; if 0, return Boot Segment default session , And no longer judge App Valid marks , No more attempts to enter App paragraph .

4*. App If a program receives a programming session request , function boot The sign reads 1 , Execute immediately ECU Reset , This will re-enter boot This program .

notes ： from BOOT Jump in APP Before you need to judge APP Data integrity , For example, to CRC check .

5 The problem is
Q: If it's burned, it's bad App This program , Can't return boot What about the segment program ？

A: Refer to the startup mode of the computer , stay ECU After power on , Set aside a short period of time to maintain boot state , In the meantime , If the specified message is received （ such as , The computer is pressed F8）, Then don't jump to App It's a paragraph .

Q: function boot Logo and App Valid signs for safety , Where should I save it ？

A: function boot Signs can be placed on RAM in , from Boot and App share .

Q: In the figure above CAN Data instance , Why did it happen twice CRC The check ？CRC Verification is the verification of which data ？

A:OEM Don't want to ECU It can be erased Flash Code for , therefore BootLoader Need to burn App Before , First erase Flash The code passed UDS Burn writing RAM in , Let's do it after burning 31 Under service CRC check . After burning ECU Of App Program ,App It may be downloaded in many segments due to discontinuous addresses . After downloading, you need to do a general CRC check . No matter which calibration ,CRC The verified data is the data segment of the code , namely 36 Valid data transmitted in the service .