JTAG
[SSinyagin] I'm trying to get use of JTAG for U-Boot debugging and probably FPGA debugging in the future. This page is not yet finished, and the work is in progress.
Building a JTAG connector for apf27Dev board
First you need a decent JTAG connector. The description below produces a 20-pin male JTAG connectior with standard ARM pinout.
List of material and part numbers at Conrad:
- 2x20-pin header, 2.54mm pitch (Conrad: 741973)
- ATA/IDE cable (Conrad: 971742)
- 2x10-pin IDC low profile header, 2.54mm pitch (Conrad: 743534)
- 20-way flat cable, 1.27mm pitch (Conrad: 609463)
Assembling it all together:
- Solder the 40-in header onto the J19 connector on the apf27dev board
- Cut off a ~10cm piece from the ATA cable with the 40pin plug at the end.
- Cut off ~10cm from 20-way flat cable
- Carefully attach the 20-pin header to the flat cable. The thing is easy to break and it requires some forcing. Better buy a spare piece in advance.
- Use a knife and a cutting pad and dissect the cable endings, ~3cm long. Dissect the whole width of the 20-way cable and only pins 40 to 31 on the 40-way ATA cable.
- Strip the cable endings
- Solder the two cables together, as specified below:
| ARM JTAG 20-pin cable | apf27 J19 40-pin cable |
|---|---|
| 1 - Vddh (+3.3v) | 39 |
| 2 - Vddh (+3.3v) | 39 |
| 3 - nTRST | 33 |
| 4, 6, 8, 10, 12, 14, 16, 18, 20 - Vss (ground) | 31, 34, 40 |
| 5 - TDI | 35 |
| 7 - TMS | 36 |
| 9 - TCK | 37 |
| 13 –TDO | 38 |
| 15 – nRST | --- |
JTAG Adapter
I'm using the Amontec JTAGkey adapter. It has a male 20-pin plug and a 20-way female-to-female cable which fits directly into the cable as described above. A cheaper solution would be to use the Amontec JTAGkey-Tiny and install a 20-pin female plug on on the connector cable for apf27dev.
Configuring OpenOCD
yet to be done. Basic tests show that cable works as expected, but board-specific settings need some more time to figure out.
