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TMS37157: Problem with wireless sensor demo: no register read when using demo software

Lennart Klaver
Prodigy 30 points
Part Number: TMS37157


Hi there!

We build the circuit from "Low-Power Battery-Less Wireless Temperature and Humidity Sensor for TMS37157", it works but partially.
- Using the USB debugger from the EZ430-TMS37157 kit I can read temperatures from the sensor, so I2C works properly.
- When I upload the "Palfi Embedded Demo" firmware (without temperature sensor code) I can read registers from our pcb using RF.
- When I upload the "MSP430F22x4 + TMS37157 + SHT21 Wireless Sensor Application" I cannot read the registers using RF anymore.

I'm kind of stuck, it looks like a power issue but I do not know where to look anymore..

When using the "no sensor firmware", RF works and the voltage at pin VCL looks like this:

When using the TI sensor software, RF reads result in CRC error and the VCL voltage looks like this:

The schematics:

Densor.pdf

Some thoughts about a direction to look into??

  • 0
    TI__Guru* 91206 points
    Lennart -
    your screen captures did not make it on the post, but your schematic did. (BTW you mis-labeled VCL as VLC on your schematic)
    could you try to re-insert those and also before you do that - try mounting the 0.47uF cap on the VBAT line. (also have that labeled as 470p on C2, but note you put in there shows 470nF, which is correct, but is also 0.47uF)

    anyway -
  • 0 in reply to Josh Wyatt
    Prodigy 30 points
    Hi, the screenshots are added to the previous post. I will try the extra capacitors.
  • 0 in reply to Josh Wyatt
    Prodigy 30 points
    Sorry, unfortunately there is no improvement. It looks like the temperature sensor power load is too much for the circuit, but it shouldn't be as the provided TI demo circuit is the same. My plan is to increase the 10uF capacitor to 20uF and change the base station burst time, but it is a long shot. Any other ideas?