PGA450Q1EVM: Pin of Rxd and Txd and range table

Hi WonGeun Yoo,

1. Only the TxD pin can be re-purposed as a GPO.
When initializing the ports in the "PGA450_init.c" file, the following example will configure the TxD pin a strong pull-up mode mode and output a low-logic:
// * INITIALIZE PORTS *
GPIO1 = 0;
GPIO2 = 0;
TxD = 0;
RxD = 1;
LSGA=0;
LSGB=0;
LINTX=0;
GPIO_CTRL=0x76; // TX-Strong (UARTTX_CONFIG=1), GPIO2-Strong, GPIO1-Strong
Then, to toggle the GPO low or high, use the following command:
TxD = 0; // low logic
or
TxD = 1; // high logic

2. I cannot provide specifics on the maximum and minimum range given the large number of variables (transducer SPL, transducer sensitivity, FOV, maximum drive voltage, matching circuit effectiveness, target properties, etc.). However, assuming you were using a transducer with identical properties, you can apply the following relation:
↑ Frequency :: ↑ Resolution :: ↑ Narrower Directivity :: ↑ Attenuation :: ↓ Distance
Thus, a 40kHz transducer will likely have a longer maximum range, but also a larger decay time. An approximation of the range may be:
Minimum = 30cm, Maximum = 7m

3. To achieve a range of 10cm~3m, you should use a higher frequency transducer. You can experiment with a transducer in the range of 70~80kHz or 180~240kHz. See the list of transducers at e2e.ti.com/.../620399
If you find one of these transducers of interest, let me know, and I may be able to advise how effective it is for your application.

4. Yes, C20 is a transducer tuning capacitor for the PGA450Q1EVM. You can attempt to modify this capacitor value between 0.1nF to 2nF, and also consider adding a damping resistor at a value between 1k-20kOhm in parallel to transducer. The matching circuit is depicted and described in the PGA460 Ultrasonic Module Hardware and Software Optimization app note ( www.ti.com/.../slaa732 ).

Hi WonGeun,

No, the RxD pin cannot be re-purposed as a GPIO.