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Altera_Forum
Honored Contributor I
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Read data through USB blaster

I have this custom board that has no JTAG connector (set up for Active Serial with an EPCS4 flash). I can load a NIOS2 on it using tricks learned in this forum and I can flash LEDs on board. Is there a way to send data back and forth for debugging (like on the JTAG UART) using SPI on the USB Blaster? 

 

Thanks
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3 Replies
Altera_Forum
Honored Contributor I
74 Views

 

--- Quote Start ---  

I have this custom board that has no JTAG connector (set up for Active Serial with an EPCS4 flash). I can load a NIOS2 on it using tricks learned in this forum and I can flash LEDs on board. Is there a way to send data back and forth for debugging (like on the JTAG UART) using SPI on the USB Blaster? 

 

--- Quote End ---  

 

You just commented that you have no JTAG connector, so what use it the USB-Blaster, as you have no way to connect it? 

 

If you're just asking whether you can "re-task" your USB-Blaster as an SPI GPIO, then yes, you can do that. Its not "officially" supported, but the FTDI drivers allow you to access a USB-Blaster, and so long as you send it USB-Blaster protocol packets, you can use it for whatever I/O you like. You do need to power the VCC pin on the 10-pin header (since that powers the buffer inside the USB-Blaster). The USB-Blaster protocol is documented here: 

 

http://sourceforge.net/apps/mediawiki/urjtag/index.php?title=cable_altera_usb-blaster 

 

Its actually less of a hassle to just use an FTDI C232HM/HD cable in MPSSE mode ... they're $26 ... 

 

http://www.digikey.com/product-detail/en/c232hm-ddhsl-0/768-1106-nd/2714139 

http://www.digikey.com/product-detail/en/c232hd-ddhsp-0/768-1011-nd/2767783 

 

Cheers, 

Dave
Altera_Forum
Honored Contributor I
74 Views

ok, I should have been more clear. I do have a 10pin connector on the board, but the JTAG lines to the FPGA (TCK, TMS, etc) are grounded. I program in active serial mode. But then I have no way of sending data back and forth. Hence my thought to repurpose the blaster as a generic SPI IO. Seems like is doable based on what you said, so I guess there is some reading in my future.  

 

Thanks!
Altera_Forum
Honored Contributor I
74 Views

 

--- Quote Start ---  

ok, I should have been more clear. I do have a 10pin connector on the board, but the JTAG lines to the FPGA (TCK, TMS, etc) are grounded. I program in active serial mode. But then I have no way of sending data back and forth. Hence my thought to repurpose the blaster as a generic SPI IO. Seems like is doable based on what you said, so I guess there is some reading in my future.  

 

--- Quote End ---  

 

 

The problem you will have is that the Active Serial signals on the 10-pin header are connected to the EPCS configuration EEPROM. You will not be able to "re-purpose" chip-select, since it is already in use by the EPCS device. 

 

If you have other FPGA pins connected to a 100-mil header, then I would recommend using those pins. You can still use the USB-Blaster, but you will avoid possible conflicts with the AS interface. 

 

Cheers, 

Dave
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