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UART Pinout

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By mali100, Senior Member on 10th June 2012, 03:39 PM
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I finally found some time to inspect the NST board for a spare UART and the search was successful!

The serial port can be accessed on U2713, pin 2 is RX, pin 3 is TX, device node is /dev/ttyS1.

I use it with a 3.3V USB-to-UART adapter, but any voltage between 1.2 and 3.6 should be fine, thanks to the TI voltage-level translator TXB0104.

There is also a second uart connected to J151 (ttyS0), but that one has no voltage-level-translator and runs with 2V. (TX is on pin 9 of J151, no idea where RX is).

I'm still trying to redirect the boot console to ttyS1, i think i have to recompile uboot.

/edit:
Patching u-boot worked, I have the boot console on ttyS1.
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Last edited by mali100; 10th June 2012 at 04:20 PM. Reason: added patched uboot
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10th June 2012, 06:07 PM |#2  
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Good job!

I wanted to look for this sometime, but you beat me to it.

ttyS0 is for the (cell phone) radio
ttyS1 is for the Bluetooth.

Could the connector place there be for JTAG?
10th June 2012, 10:33 PM |#3  
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Quote:
Originally Posted by Renate NST

Good job!

I wanted to look for this sometime, but you beat me to it.

I wanted to do this since my last failed kernel porting attempt. I hope it helps me debugging non succesfully booting configurations.

Quote:

ttyS0 is for the (cell phone) radio
ttyS1 is for the Bluetooth.

Is that an actual android standard, or just some leftovers from the reference platform the nst and nook color are based on (the remains in the init.rc)?

Quote:

Could the connector place there be for JTAG?

I think the JTAG is more probably on J151 together with ttyS0, than on U2713.
ttyS0 was the standard console, and it would make more sense that the J151 was used as debug-port.
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11th June 2012, 12:13 AM |#4  
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Quote:
Originally Posted by mali100

The serial port can be accessed on U2713, pin 2 is RX, pin 3 is TX, device node is /dev/ttyS1.

I use it with a 3.3V USB-to-UART adapter, but any voltage between 1.2 and 3.6 should be fine, thanks to the TI voltage-level translator TXB0104.

Mali,
My USB-to-UART adapter needs 3.3V (to set “upper voltage” level)
Could you help, where can I get in on Nook board?
11th June 2012, 12:46 AM |#5  
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Quote:
Originally Posted by Renate NST

ttyS0 is for the (cell phone) radio
ttyS1 is for the Bluetooth.

Do you know any devices that can be connected to this ports? It would be great to enable only Bluetooth or even cell phone.
11th June 2012, 11:28 AM |#6  
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Quote:
Originally Posted by ApokrifX

Mali,
My USB-to-UART adapter needs 3.3V (to set “upper voltage” level)
Could you help, where can I get in on Nook board?

You can use pin 1 of U2713, it's connected to VCCb on the TXB0104. Altough the voltage is disabled when the nook sleeps, but that shouldn't be a problem.
12th June 2012, 04:51 AM |#7  
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Quote:
Originally Posted by mali100

You can use pin 1 of U2713, it's connected to VCCb on the TXB0104. Altough the voltage is disabled when the nook sleeps, but that shouldn't be a problem.

Ok... But it's gotta be 3.3V somewhere, right?
15th June 2012, 07:22 PM |#8  
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Quote:
Originally Posted by ApokrifX

Ok... But it's gotta be 3.3V somewhere, right?

Quick! Break the laws of physics and pull power from a penny!
9th December 2012, 10:36 PM |#9  
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I haven't had a driving need to use this until I tried an upgrade to 1.2 and got a boot loop.

There are various versions of u-boot.bin.
The easiest way to patch it is to simply search for ttyS0 and replace the two occurrences with ttyS1.

ttyS0 appears also in env.txt inside uRamdisk (and uRecRam).

I found a old fax that has the 10 pin connector that fits on the Nook.
I might try to put it on. For now I have the soldered wires.

In any case, the 1.2 boot loops and the last message is:
Code:
binder: 988:1039 transaction failed 29189
I've screwed with a lot of things on my Nook, but the "update" should have wiped about everything.
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11th December 2012, 01:08 AM |#10  
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Just a short update:
I soldered in the connector successfully. It looks nice.
The level converter to standard 9 pin "RS-232" is simple and cheesy, 2 resistors and a transistor.
It works fine though. I can see the boot up.
After that I can switch to logcat over ADB over USB.
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12th December 2012, 01:00 AM |#11  
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Here's a really poor photo of my setup.
My next cell phone must have auto-focus and macro mode.
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