Can JTAG be remapped?

perryc
Posts: 25
Joined: Fri Feb 17, 2017 1:29 am

Can JTAG be remapped?

Postby perryc » Mon Mar 20, 2017 3:27 am

I see info in the tech_ref that suggests JTAG can be remapped with Direct I/O via IO_MUX. Section 4.4.2 is a bit thin but I'm not seeing alternate pads that can accept MT* functions.

Perry

sintech
Posts: 27
Joined: Wed Dec 14, 2016 2:54 pm

Re: Can JTAG be remapped?

Postby sintech » Tue Mar 21, 2017 7:05 am

Yes, I'm also curious about it, especially when MT pins are used for SD functions.

ESP_Angus
Posts: 2344
Joined: Sun May 08, 2016 4:11 am

Re: Can JTAG be remapped?

Postby ESP_Angus » Tue Mar 21, 2017 8:06 am

Unfortunately JTAG cannot be remapped.

sintech
Posts: 27
Joined: Wed Dec 14, 2016 2:54 pm

Re: Can JTAG be remapped?

Postby sintech » Tue Mar 21, 2017 9:40 am

Then maybe SD signals can be remapped to other pins?
Is there any expected performance degradation?
Thanks in advance.

ESP_Angus
Posts: 2344
Joined: Sun May 08, 2016 4:11 am

Re: Can JTAG be remapped?

Postby ESP_Angus » Tue Mar 21, 2017 10:12 am

Unfortunately SD can't be remapped either. These (& EMAC) are almost the only peripheral pins which are fixed, sorry.

perryc
Posts: 25
Joined: Fri Feb 17, 2017 1:29 am

Re: Can JTAG be remapped?

Postby perryc » Tue Mar 21, 2017 12:58 pm

Well this is not good news (but glad it was not a dumb question). I've got a uSD card in my design as well so what's the best practices plan here when you need a file system?
I ironically I got motivated to figure out JTAG so I could debug my attempt to get SPIFFS working. I'm thinking the best I can do is:
1) JTAG header and uSD share IO12-IO15 in next HW version
2) Get SPIFFS Working
3) When needing to do serious bug hunting, pull uSD Card, build a SPIFFS version of my firmware and then JTAG should work.

Sure hope those JTAG pins do not mind 10K pullups or I'll need to add a jumper block.

Perry

sintech
Posts: 27
Joined: Wed Dec 14, 2016 2:54 pm

Re: Can JTAG be remapped?

Postby sintech » Tue Mar 21, 2017 2:16 pm

In my opinion, adding SPI support to sdmmc driver will partially solve this issue of SD and JTAC coexistence.
Because SPI signals can be remapped and even the default VSPI pins are not mixed with other useful signals.

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