OpenWrt Forum Archive

Topic: Serial Garbage from WR1043ND

The content of this topic has been archived on 27 Mar 2018. There are no obvious gaps in this topic, but there may still be some posts missing at the end.

My 1043ND it's dead after upgrading from the last trunk and I got this USB serial interface that give me nothing but garbage on the screen. The adapter it's made of a Silabs CP2102 and a Texas Instruments MAX3243.
http://i.imgur.com/yd6CYfm.jpg

The schematic of this board it's very similar to this: (Source)
http://i.imgur.com/pezkAGo.gif

Or this one. (PU232S)

Set all setting to 115200 8N1 and set Flow Control to None, but still I get garbage characters on putty or termite.

Searched all over and found nothing useful on Google or on this forum, already tried to apply all this solutions, without any success:

- Check ground condition.
- Use short cables (mine is less than 10cm and shielded).
- 10K Resistor pullup from VCC at TX (router side).
- add a 10R jumper at TX and RX (router side).
- Isolate the shield ground from data ground.
- Lift pin 26 and feed MAX3243 with 3.3V from router instead of 5V.
- Feed MAX3243 with 3.3V from CP2102 pin 6.
- Try every baud rate possible from 300bps to 921600bps.
- Use a different driver.
- Use Linux 'screen' software.

Did I miss something?
What else can be done?

Thank you.

(Last edited by katananja on 19 Jul 2013, 16:10)

Are you connecting your router to the outputs of the MAX3243? If so, then that's why you see gibberish.

The serial link in your router is a TTL-level serial interface, and the schematic you give is for a USB to RS-232 interface. RS-232 operates on different voltage levels, so your serial converter consists of two chips: one that is the serial interface, and one that converts TTL levels to RS-232 levels (the MAX3243).


You can test your link by connecting TX and RX together. You should see your own text  repeated in putty.

To make it work with your cable, you need to connect the router link to pins 25, 26 and 3 of IC1 and remove IC2 (or at least remove traces for pins 25 and 26.  Now hope that those pins in your router have ESD protections that prevented that +10 V from frying your serial port..

Worked like a charm @gerritb, thanks.

U-Boot 1.1.4 (Apr 28 2011 - 15:55:09)

AP83 (ar9100) U-boot 0.0.11
DRAM:  
sri
32 MB
id read 0x100000ff
flash size 8MB, sector count = 128
Flash:  8 MB
Using default environment
In:    serial
Out:   serial
Err:   serial
Net:   ag7100_enet_initialize...
No valid address in Flash. Using fixed address
: cfg1 0xf cfg2 0x7114
eth0: 00:03:7f:09:0b:ad
eth0 up
eth0
Autobooting in 1 seconds## Booting image at bf020000 ...
   Uncompressing Kernel Image ... OK

Problem solved!

(Last edited by katananja on 19 Jul 2013, 22:05)

The discussion might have continued from here.