- Wed Mar 16, 2011 7:41 pm
#122953
So first, the questions about the OBD-II-UART. Looking at the Eagle files for the board, it appears that the NC pins are not connected. However, on my board, with power applied, I get about 4.7V on the NC pins. I am asking as I managed to fry my board somehow. This leads into the Bluetooth Mate question. I got the Bluetooth mate to plug into the PC side interface port on the OBD-II-UART. When plugged directly in, it would not send to the OBD-II board. However, when connected via a cable with RX,TX,and GND, it worked just fine.
So my assumption was that the RTS/CTS flow control pins on the BT Mate were the problem. The RN-42 docs state that they should be shorted together if using a 3 conductor cable. The BT mate board provides a bridge on the bottom of the board that will connect the two signals, so I put a solder bridge there.
Thinking about it now, I wonder if using that bridge is the correct thing to do, or if I should have jumped the RTS and CTS pins on the header instead. I plugged the BT mate into the OBD-II board after bridging the CTS/RTS signals as in the picture above, and the latter board never worked again. It will not initialize at all. I checked all the supply voltages and they are fine. There is no signal on either osc line to the ELM327. I get a very faint output on the RX LED as you can see below.
So, I am pretty sure I killed it. At one point, after failure, it did go through the init sequence. I was doing a "quick and dirty" temperature check on the ELM327 (touched it with my finger tip). No idea what caused it to init properly at that point. It only did it once.
This brings me full circle back to the NC pins on the OBD-II board. I had put in a spaghetti wire to provide +5V to the header to power the BT Mate board. You can see in this picture.
After killing the board, I started checking the NC pins and it turns out they are connected to something. Pin 1 (GRN) shows about 10k to ground and pin 5 shows about 15k to ground. Pin 4 is jumpered to +5V as shown above.
So, three basic questions:
1) Do you jumper RTS/CTS on the Bluetooth Mate at the solder bridge provided or at the header pins?
2) What are the NC pins on the OBD-II-UART board actually connected to?
3) What killed my OBD-II-UART board? Was it the bridging of CTS/RTS on the BT Mate? Problems with the +5V jumper? Static? Martians?
Thanks for any insight anyone can provide.
So my assumption was that the RTS/CTS flow control pins on the BT Mate were the problem. The RN-42 docs state that they should be shorted together if using a 3 conductor cable. The BT mate board provides a bridge on the bottom of the board that will connect the two signals, so I put a solder bridge there.
Thinking about it now, I wonder if using that bridge is the correct thing to do, or if I should have jumped the RTS and CTS pins on the header instead. I plugged the BT mate into the OBD-II board after bridging the CTS/RTS signals as in the picture above, and the latter board never worked again. It will not initialize at all. I checked all the supply voltages and they are fine. There is no signal on either osc line to the ELM327. I get a very faint output on the RX LED as you can see below.
So, I am pretty sure I killed it. At one point, after failure, it did go through the init sequence. I was doing a "quick and dirty" temperature check on the ELM327 (touched it with my finger tip). No idea what caused it to init properly at that point. It only did it once.
This brings me full circle back to the NC pins on the OBD-II board. I had put in a spaghetti wire to provide +5V to the header to power the BT Mate board. You can see in this picture.
After killing the board, I started checking the NC pins and it turns out they are connected to something. Pin 1 (GRN) shows about 10k to ground and pin 5 shows about 15k to ground. Pin 4 is jumpered to +5V as shown above.
So, three basic questions:
1) Do you jumper RTS/CTS on the Bluetooth Mate at the solder bridge provided or at the header pins?
2) What are the NC pins on the OBD-II-UART board actually connected to?
3) What killed my OBD-II-UART board? Was it the bridging of CTS/RTS on the BT Mate? Problems with the +5V jumper? Static? Martians?
Thanks for any insight anyone can provide.
