LDC1000 External Clock

My LDC1000 Eval Module arrived and I've plugged it all in and so far been very impressed with the results.

Now I need to try to integrate it into my own microcontroller application, so I carefully broke it into its 3 sections on the perforated line, installed pins & sockets, and then plugged it all back together to check that I hadn't damaged anything - still working perfectly.

So, next step - I hooked it up to an SPI  port on my micro, copied all of the register values as shown in the Eval GUI and used these to initialize the LDC1000, and gave it a 6MHz clock (as this is what the MSP430 on the Eval Module is doing).

All I manage to read out from the data registers at 0x21 - 0x25 is 00000 ...

After many hours of frustration and fiddling with register values I discovered the following: If I  turn off the 6MHz clock I get sensible results from register pair 0x21,0x22 . If I turn it back on I get 00000! This even applies to reading the config registers - clock on and I read back 0000, clock off and I read back exactly what I put there!

I would really appreciate it if anyone at TI could give a little help here ...

My project for tomorrow is to try multiplexing a handful of sense coils (using a fairly good analog Mux IC) as my final application needs to measure upwards of 40 of them. I do realize there will be a hit on the sample rate due to settling after switching ... For now the results from the prox registers at 0x21, 0x22 will be good enough, but I'd really like to have the rest of the data too.

If it helps, these are the values I'm initializing my LDC1000 with:

{0x12, //  Rp MAX @ 0x01
0x3b, // Rp MIN @ 0x02
0x94, // Sens Freq @ 0x03
0x17, // LDC Config @ 0x04
0x00, // Clk Config @ 0x05
0x50, // Comp Thr High LSB @ 0x06
0x14, // Comp Thr High MSB @ 0x07
0xc0, // Comp Thr Low LSB @ 0x08
0x12, // Comp Thr Low MSB @ 0x09
0x00, // INTB pin Config @ 0x0a
0x01}; // Power Config @ 0x0b

Hi Bruce,

What is your VIO voltage?  How are you feeding the 6MHz clock?

Thanks,

Chuck

Hi Chuck,

My VIO & Vdd are both 5V and I'm driving the 6MHz clock directly from a port pin on my microcontroller. My 'scope says its a nice 50% duty-cycle square wave.

 - Bruce

Oops ... my bad ...

Micro is running on 3.3V and therefore obviously my 6MHz clock & SPI are also at 3.3V

Moved the LDC's VIO to the micro's 3.3V supply and now all appears happy.
Thanks for pointing me in the right direction.

 - Bruce

Glad you got it working, Bruce :-)

Please keep us posted on your progress; we'd like to see what you end up doing with our part!