Helpful ReplyCannot loopback UART with RN42-SM Socket module

Author
wygonski
New Member
  • Total Posts : 2
  • Reward points : 0
  • Joined: 2011/01/26 11:04:11
  • Location: 0
  • Status: offline
2014/07/16 15:26:58 (permalink)
0

Cannot loopback UART with RN42-SM Socket module

I am using the UART (not RS-232) interface on the RN-42-SM Socket Module.  My initial goal is to do a loopback test sending characters at 115200 from PC over Bluetooth connection, looping back from Tx to Rx on the RN-42, and back to PC over Bluetooth.
I modified the board as follows:
1.  Removed R6 and R8
2.  Connected CTS and RTS on Header B (tied J1-3 to J1-4)
3.  Connected Tx and Rx on Header B (tied J1-1 to J1-2)
4. Supplied power:  3.3V on Header A pin 11;  GND to Header A pin 12

I can open a connection using a PC terminal emulator to the BT COM port at 115200 baud, and the green LED goes on steady when this is done.   When I type characters in the terminal emulator, I see them with a scope probe on the RN-42 UART Tx-Rx pins, and the bit time corresponds to 115200.   However, the characters are not returned back over the BT connection.   I noted that the voltage level on the Tx-Rx pins is only 2V when high, which is below the minimum 2.8V
 
Can anyone help with what the problem may be?
 
Thanks in advance,
John
#1
Jordi Gonzalez
New Member
  • Total Posts : 2
  • Reward points : 0
  • Joined: 2014/07/21 04:03:27
  • Location: 0
  • Status: offline
Re: Cannot loopback UART with RN42-SM Socket module 2014/07/21 11:11:04 (permalink) ☄ Helpfulby wygonski 2014/07/23 07:00:31
0
Hi!
Try to connect CTS with GND. If CTS it's not connected to GND then UART doesn't work!
Make sure that you connect Rx of PIC with Tx of RN42.
Then when you program the PIC if UART is in PORTB, make sure that Tx is an output, and Rx and input.
 
Good luck!
post edited by Jordi Gonzalez - 2014/07/21 13:37:12
#2
wygonski
New Member
  • Total Posts : 2
  • Reward points : 0
  • Joined: 2011/01/26 11:04:11
  • Location: 0
  • Status: offline
Re: Cannot loopback UART with RN42-SM Socket module 2014/07/23 07:03:22 (permalink)
0
Thanks for the reply.  I connected RTS and CTS as recommended by RN, and verified that CTS is low as required, so that's not the problem.  By now I'm concerned with the fact that TX-RX voltage level is only 2V.
#3
Jump to:
© 2017 APG vNext Commercial Version 4.5