P82B715TD Extended MPU-6000

Software Python
1

I have MPU-6000 sensor that I need to have about 12 feet from my RaspPi. I am using P82B715TD to extend the IC2, however I am running into an issue.

When I plug the MPU-6000 directly into my IC2 interface on the PI, I am able to run the sample code.

When I plug through the extender I get:

Traceback (most recent call last):
File “test_gyro.py”, line 18, in
bus.write_byte_data(0x68, 0x1B, 0x18)
File “/usr/local/lib/python3.5/dist-packages/smbus/util.py”, line 59, in validator
return fn(*args, **kwdefaults)
File “/usr/local/lib/python3.5/dist-packages/smbus/smbus.py”, line 145, in write_byte_data
raise IOError(ffi.errno)
OSError: 121

So a few questions:

  1. Does my smbus address stay the same with an extender? or do I need to use a different bus address when going through an extender?

  2. Here is my physical layout, am I doing something wrong here?

I have a Power supply of 19 volts (the extender supports this), I have a 4 wire connection extended piece, Red, black, green, yellow. This is not the same as the premade 4 wires cables.

From the PI I have the 4 wire connector that came with the sensor plugged into the Extender TX side. Then from Extender TX, I have a 19 volt DC plugged into the barrel connector on the TX, From here I have the Red wire in the 4 wire extended wire also plugged into the + on the barrel plug. On the TX side I have G on the Black, 1 is the Green wire, and 2 is the Yellow wire. The TX has a red LED that is lit.

Ok the 4 wire connector connects to the RX side of the extend. Green is plugged into 1, Yellow into 2, Black into G and R goes to a barrel connector (no ground on the barrel connector as I tested the G and the minus on the Barrel is the same) So at this point, the standard four wire connector goes from the RX extender to the MPU-6000 “in” At this point, all of the pieces have a RED light on, so I think Power is ok? Am I missing something big here?

Any advice would be helpful!

John

2

So I found i2cdetect, and see that there are no devices found when connected through the extenders… Thoughts?

Through extender:
$ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- – -- – -- – -- – --
70: – -- – -- – -- – --

Direct connect:
$ sudo i2cdetect -y 1
0 1 2 3 4 5 6 7 8 9 a b c d e f
00: – -- – -- – -- – -- – -- – -- –
10: – -- – -- – -- – -- – -- – -- – -- – --
20: – -- – -- – -- – -- – -- – -- – -- – --
30: – -- – -- – -- – -- – -- – -- – -- – --
40: – -- – -- – -- – -- – -- – -- – -- – --
50: – -- – -- – -- – -- – -- – -- – -- – --
60: – -- – -- – -- – -- 68 – -- – -- – -- –
70: – -- – -- – -- – --

3

I am going to embarrassingly answer my own question. Fun fact, when you buy a pair of extenders, you do indeed get two TX and two RX modules. If you grab two RX modules and try to make them talk, you will fail. In fact you will fail with the message I listed above! If, however, you are not an idiot like me, and you use a TX AND and RX module… you do in fact having a working extender with the hardware layout I presented above. I apologize for any bother.

John

4

No problem John. Glad you figured it out.