The cheap clone was never able to get reliable contact. While the Terasic was rock solid in its communication with the Color3 board. The suffix is really different, with 6 clock clocks but also a fast clock group in between. In the middle we have the expected 16 fast clock groups. We have a prefix with 8 slow clocks, but in between the second and the third slow clock, there's a signal fast clock group. We see a similar pattern, but interestingly enough, it's not the same. The set of signals below that is a slightly zoomed in version of the one above. Cheap Clone USB BlasterĪnd here's the equivalent of the cheap clone. In addition, there are roughly 3 idle cycles between a fast clock group. Meanwhile, during a fast clock group, the clock toggles at 6MHz. This is expected: according to the Altera documentation, 6MHz is exactly what one can expect from a USB Blaster. When you zoom in on the slow clock cycles, you can measure a TCK frequency of 780kHz: And at the end you have a suffix with 2 slow clock cycles.įor this investigation, it doesn't matter what gets transported when, but it's almost certain that the slow clock cycles are used to move the JTAG TAP from iDLE state to the scan DR or scan IR state, and that the fast clock groups are used to rapidly scan data in and out of a scan data register. In the middle there are 16 groups with fast clock cycles (each group is itself 8 clock cycles). There are 3 major sections: during the prefix there are 8 slow clock cycles. The most important signal here is TCK, in yellow. This is the first transaction that travels over the JTAG cable when you issue the "nios2-terminal" command. So let's look at the signals as measured on the JTAG connector of the Color3 board. The Chinese clone contains an STM32F101 micro controller.Īs I wrote earlier, the biggest issue with the cheap clone is that it doesn't work on my eeColor Color3 board. The Terasic version is supposed to be an Altera sanctioned design that has a chip USB to parallel converter chip from the FTDI family, and a small CPLD that converts the parallel data into JTAG (and some other formats). Since I don't have a microscope (yet) to solder some really tiny wires on the TQFP144 of the SiI9233 (I want to record all I2C transactions to see how the thing gets configured), I decided to have a closer look at the difference between a high quality $50 Terasic USB Blaster and the cheap $3 Chinese clone that's available on AliExpress, eBay etc. I had an urgent need to measure something meaningful. I was supposed to work on getting the SiI9233 up and running, but UPS delivered a nice package today:
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