Recently a friend of mine gave me a brand new Olimex AVR-MT-128 board in order to develop a custom application for him. I have an AVR-USB-JTAG which I bought long time ago and I have successfully used it before. The AVR-MT-128 board is preloaded with some kind of demo application by Olimex and it is working just fine. But the problem is I cannot connect my JTAG debugger to the MCU of the board. Using other boards I have developed myself there is no problem. When trying to connect to AVR-MT-128’s MCU the AVR Studio says it has detected the OCD JTAG adapter but the target device did not return a valid JTAG ID.
Does anyone have a clue what could the problem be?
Is it possible that when producing the board Olimex has disabled JTAG through the JTAGEN fuse although they should not normally do this. I have not tried programming the board through ICSP.
I’ve never used JTAG, but found this in the data sheet.
To be able to use the JTAG interface, the JTAGEN Fuse must be programmed. The device is default shipped with the fuse programmed. In addition, the JTD bit in MCUCSR must be cleared. Alternatively, if the JTD bit is set, the External Reset can be forced low. Then, the JTD bit will be cleared after two chip clocks, and the JTAG pins are available for programming.
If this is the case, you can’t use the JTAG for debug or boundary scanning. It can only be used for programming.
I wish I could be more help, but I use AVRISP and have an VP-380 to correct fuse mistakes.
Is it possible that when producing the board Olimex has disabled JTAG through the JTAGEN fuse although they should not normally do this. I have not tried programming the board through ICSP.
Thanks and regards!
Its possible , that the jtagfuse is disabled.
I do that on Mega16/32 else 5 of the pins on Port C , can’t be used.
Well i could disable jtag in software , but this is easier 8)
If you have an ISP programmer , you could restore the JTAGEN fusebit
The JTAGEN fuse was DISABLED !!!only ISPEN fuse was ENABLED
Probably, the people from mass production working with ISP programmer only in order to put some demo into the board, and nobody ENABLES the JTAGEN fuse !!