Question 1

What does the DAC Signal Transmitter do?

Accepted Answer

It converts a digital integer (1–9) into an 8-bit DAC analog voltage using a 5V reference (DAC formula: V = (input / 255) × 5). It can also apply Nyquist sampling at 18Hz to generate a full sine-wave payload, then transmit everything to a satellite endpoint via HTTP POST.

Question 2

What is the voltage formula used?

Accepted Answer

V_out = (digital_input / DAC_MAX) × V_ref, where DAC_MAX = 255 (8-bit) and V_ref = 5.0 V. For example, input 5 yields V = (5/255) × 5 ≈ 0.0980 V.

Question 3

How does Nyquist sampling work here?

Accepted Answer

The sampling frequency is fixed at fs=18Hz. According to Nyquist's theorem, this correctly reconstructs signals up to 9Hz — exactly matching the maximum allowed input of 9. For each frequency f, 18 samples are taken of sin(2π·f·t) and converted to DAC values.

Question 4

What HTTP protocol is used for satellite transmission?

Accepted Answer

The transmitter sends a JSON payload via HTTP POST containing: digital_input, binary (8-bit), dac_voltage, signal_type (single or sampled), and optionally the full Nyquist sample arrays. The server logs the transmission and returns an ID with DB confirmation status.

Question 5

Can I see recent transmissions?

Accepted Answer

Yes. The page shows the last 20 transmissions including ID, input value, signal type, voltage, timestamp, and database save status (DB ✓, PENDING, or ERROR).