In-system recovery with bootloader v3
In-system update of the bootloader
The firmware can be updated from within the X16 without any external tools:
- Download SMCUPDATE-x.x.x.PRG, where x.x.x is the SMC firmware version
- Copy the file to your SD card and insert the SD card into your X16
- LOAD the SMCUPDATE-x.x.x.PRG program and RUN it
- The new firmware is embedded into the program and you need no other files
- Follow the on-screen instructions
The update procedure differes slightly depending on which bootloader version is installed on your SMC.
If your SMC has bootloader v1 installed the SMC enters into an infinite loop after finishing the update. Just disconnect the X16 from mains power, wait until the LEDs go out, and then reconnect the X16 again.
There are no known issues with bootloader v1.
Bootloader v2 differs from v1 in that the SMC will reset and power off after finishing the update. There is no need to disconnect the computer from mains power.
Some production boards were delivered with a corrupted version of bootloader v2, often referred to as a "bad" bootloader.
It is almost certain that you have got the bad bootloader if
PRINT I2CPEEK($42,$8E) returns 2 (bootloader version) and
any of the following is true:
- the serial number of your X16 board is between PR00100 and PR00900
- the
HELPcommand shows that you have got SMC firmware version 45.1.0
The SMCUPDATE program will display a warning if there is a risk that you have got the bad bootloader. There is, however, no way for the program to determine for sure before the update has started.
Even with the bad bootloader, the update works until the very final stage where it enters an infinite loop instead of resetting the SMC and powering off the system.
The SMCUPDATE program will notify you at the end of the update process if you have got the bad bootloader.
If this happens it is important not to disconnect the computer from mains power. Doing that will brick the SMC firmware, requiring you to update it with an external programmer.
There is a tested procedure to make the update work with the bad bootloader. Read about it here. In short, you need to reset the SMC by connecting reset pin #10 to ground using a piece of wire.
Bootloader v3 will also reset the SMC and power off the computer when the update is done. There is no need to disconnect the computer from mains power.
Bootloader v3 is reworked to be safer than the earlier versions. It also enables the SMCUPDATE program to verify the firmware after an update.
Bootloader v3 supports recovery of the SMC even if a firmware update failed and left the SMC inoperable (bricked). This can happen, for instance, if the update process is interrupted.
The recovery update requires that you store SMCUPDATE-x.x.x.PRG on the SD card as file name AUTOBOOT.X16. If you already have a file named AUTOBOOT.X16, remember to back it up first.
Disconnect the computer from mains power and wait until the LEDs go out.
Press and hold the Reset button while you reconnect the computer to mains power. The computer will turn on and you may release the Reset button as soon as you see that the Power LED has turned on.
The computer automatically loads and runs the file AUTOBOOT.X16, which will update the SMC firmware without user interaction after a countdown.
If you want to abort you must disconnect the computer from mains power before the end of the countdown.
The SMC is reset and the computer is turned off after the update is finished. You may turn on the computer again and delete AUTOBOOT.X16.
Since SMC firmware version 47.2.0 it is possible to do an in-system update of the bootloader itself.
Use the SMC bootloader tools to do that.
WARNING: It is not recommended downgrade the bootloader from version 3 to version 2 or 1 using those tools. If you do that the SMC firmware must be updated after the bootloader downgrade but before the SMC is reset or power cycled. Otherwise, the SMC will become non-functional.
Programming the X16 with an external programmer requires that the SMC microchip is removed from the X16 board.
Ensure that the X16 is disconnected from mains power before you start, as the SMC is always powered.
To prevent damaging the X16 board, it is recommended to use an anti-static wrist band when touching the board or its components.
It is possible to program the SMC with a TL866 series programmer, but at least some of the programmers in that series have problem setting the extended fuse correctly.
It is therefore recommended to program the SMC with the commmand line utility avrdude and a programmer that is compatible with that utility.
For further information, go to the guide on recovery with an Arduino.