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CCS/TIDM-BPM: TIDM-BPM pump and valve duty cycles

Part Number: TIDM-BPM

Tool/software: Code Composer Studio

Hello,

I am interested in the TIDM-BPM device for blood pressure monitoring and I checked out the source code provided on the webiste. I was especially checking the pwm signals for the pump and valve. Here is the part of the code concerned : 

void timer0Init(void)
{
P1DIR|=BIT2+BIT3;
P1SEL|=BIT2+BIT3; //SELECT P1.2/P1.3 AS TA0 OUTPUT

TA0CCR0 = 4000; //
TA0CCTL1 = OUTMOD_7; // CCR1 toggle/set,PUMP
TA0CCTL2 = OUTMOD_1; //VALVE
TA0CCR2 = 3400; // CCR1 PWM duty cycle for valve
TA0CCR1 = HIGH_AIRIN; // for pump with HIGH_AIRIN = 2500
TA0CTL = TASSEL_2 + TACLR+ MC_1; // SMCLK, up mode,
}

My question is about the duty cycle of these two pwm signals. How the duty cycle of these pwm signals was determined compared to the inflation and deflation speed ? In other words what's the relationship used between the duty cycle and the inflation speed (for pump) and deflation speed (for valve). I mean let's say we want to reach a certain pressure of 200 mmHg in 20 s. How should we determine the duty cycle of the pump to reach this pressure in 20s ? I hope that my question is clear.

Thank you very much.

Best regards,

Mike

  • Hi Mike,

    The section17.2.5.1 of the device User's Guide gives you details about the PWM output configuration for different mode.

    Also, you could refer to the Peripherals Example code for the device, which including codes for PWM output.

    http://dev.ti.com/tirex/explore/node?devices=MSP430F6638&node=AKdBlqImUz6tvVbABDpt4g__IOGqZri__LATEST

  • Hi Zhao,

    I think you didn't really understand my question. My question wasn't about the pwm output configuration for different mode. My issue isn't about how to program a pwm. My question concerns the TIDM-BPM device and especially the source code provided for this device. This device is for blood pressure monitoring, and we need for a blood pressure monitor a pump and a valve. Both are driven by a pwm signal. And my question is about the relationship between the duty cycle of these signals and the pump speed (inflation speed). In others words if for example we want to reach a 200 mmHg pressure in the cuff in 20 seconds, what should be the duty cycle of the pwm signal of the pump ? How to determine it ? And how in the source code provided above the value of 3400 was chosen for the duty cycle of the pump (why 3400 over 4000 and not 2700 or 3000 for example ? Is this clearer ? 

    Thank you.

    Best regards,

    Mike

  • Hi Mike,

    The pump is controlled by the output CN5 of on the board. And the CN5 should be related, or synchronized, to the PWM signal on PUMP(Pin 36 of the MCU). The relationship between the PWM output of MCU and pump speed should depend on the pump itself as well as the other pressure parts to the pump.

    I have no idea since I don't have the pump and pressure parts. But you may test and determine the PWM duty cycles for your used pump.

  • Hi Zhao,

    Thank you for your help.

    Regards,

    Mike

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