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MSP430F1121: Reading data from 3.5mm audio jack and Soft Modem demo

Will Kleinberg
Intellectual 570 points
Other Parts Discussed in Thread: MSP430F1121

I wonder if it'd be a relatively straightforward exercise to read data from a 3.5mm audio jack using a MSP430F1121 and a raspberry pi. Essentially, I'm trying to get the PI to send audio commands to control a motor with a MSP430. I know I could use USB, but I wanted to control MSP430 with javascript. The communication will be unidirectional: raspberry pi transmits data as audio output to MSP, so the MSP will do the reading. Does anyone know if this could be accomplished by using the Soft Modem demo at http://www.ti.com/lit/an/slaa204/slaa204.pdf Note that I'm trying to communicate using audio signals.

This is the circuit provided - Is it right that TX and RX are audio signals?

One more thing is that pins 6.6 and 6.7 are explicitly exposed - what are they for though?

Any help would be much appreciated.

  • 0
    TI__Guru**** 202216 points
    Hi Will,

    The MSP430 Embedded Soft-Modem Demo Application Report is quite an old application report but I'm glad to know that you might be able to find a use for it. RX+ (filtered to P2.3/CA0) and TX+ (P1.7/TA2) are the audio signals. Please note the RX/TX signal paths and limitations described in Section 3.3. P6.6/P6.7 are used as general input pins for the User Interface as described in Table 6 and are unnecessary if not using the Soft-Modem Application Demo.

    Regards,
    Ryan
  • 0 in reply to Ryan Brown1
    Intellectual 310 points

    Section 3.3.2 says "The output of the MSP430 FSK modulator on pin P1.7 (TA2) is a square-wave signal with an amplitude of 3.3V." Is TX+ really audio?

  • 0 in reply to Steve Wong
    TI__Guru**** 202216 points
    Not true audio in the form of sine waves, this application report was designed for MSP430s that might not have an on-board DAC and therefore cannot generate a true wave output. It therefore uses a PWM pin to output a modulated signal that can represent and be interpreted as audio.

    Regards,
    Ryan

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