Connect LVTTL to PIC

[shahrul]

Now, I have successful interface SKM53 with PIC. This is the final circuit.

SKM53 Schematic.jpg (23.01 KiB) Viewed 4784 times

I have try remove R3, but it not works.
I have try use R4 = 330 ohm, but it not works.
I have try use R5 = 1k ohm, but it not works.

My finding, maybe the SKM53 have high internal impedance because it doesn't matching with low impedance load.

[robosang]

Weird for me to see that, anyway I don have the GPS module, cannot investigate further,

[shahrul]

Weird for me to see that, anyway I don have the GPS module, cannot investigate further,

I'm also weird, can't explain theoretically but this is practically

[takao21203]

Have you tried PNP transistor (2n3906)?

[shahrul]

Have you tried PNP transistor (2n3906)?

No, maybe on next project.

[waiweng83]

Hi Shahrul,

I'm facing the same problem with the LS20031 GPS module from Sparkfun. AFAIK, both LS20031 and SKM53 are using the same Mediatek MK3329 Chipset.

There is an easy fix to the problem, just change the R1 to higher value. I'm using 33k ohm for now, I think everything from 30K to 100k should work.

I got to know this fix by trial and error. I still can't figure out why the low resistance will halt the GPS module.

[shahrul]

Hi Shahrul,

I'm facing the same problem with the LS20031 GPS module from Sparkfun. AFAIK, both LS20031 and SKM53 are using the same Mediatek MK3329 Chipset.

There is an easy fix to the problem, just change the R1 to higher value. I'm using 33k ohm for now, I think everything from 30K to 100k should work.

I got to know this fix by trial and error. I still can't figure out why the low resistance will halt the GPS module.

Hi Waiweng, thanks for the info. I will try later on next project.