A fast rangefinder can fit within a UART link and still lose data in the host. For an LRF50H planning case at 10 kHz, a four-byte report over 460800-baud 8N1 uses about 86.8% of the receive direction’s wire capacity. That is a calculation under stated assumptions, not a measured end-to-end performance guarantee.
Start with the documented facts and the assumptions
The current LRF50H high-rate module documentation lists a measurement frequency of 20 Hz–10 kHz, with 1 kHz as the default. Its UART section specifies 460800 baud, eight data bits, no parity and one stop bit. The output section describes a four-byte report. The throughput calculation below assumes one such report per measurement, unchanged at the selected rate. Confirm that output behavior and the rate-setting procedure for the actual firmware before relying on the 10 kHz case.
Three different quantities matter: the sensor’s measurement frequency, the number of reports it actually emits, and the number of valid reports the application consumes. A specification for the first does not establish the other two. Use a serial capture to check report length and cadence before sizing the receive path.
| Model | Documented measurement frequency | Documented UART output | Planning caution |
|---|---|---|---|
| LRF50H | 20 Hz–10 kHz; default 1 kHz | Four bytes; 460800 baud; 8N1 | Verify actual output at the selected rate. |
| LRF600H industrial module | 1 kHz or 50 Hz, automatically selected according to echo strength | Four bytes; 460800 baud; 8N1 | Do not assume a constant 1 kHz stream. |
These entries were checked against the LRF50H V3.0 and LRF600H V2.0 documents in ERDILRF’s technical library on 19 September 2026. This table compares communication inputs to the calculation, not guaranteed host performance. These documents do not specify a numerical UART logic level for these two models. Their supply-voltage specification does not establish the TX/RX signal voltage.
Count the bits that actually travel on the wire
As explained in Microchip’s UART framing guidance, asynchronous serial communication includes start and stop framing around the data bits. With 8N1, each data byte consumes ten bit periods: one start bit, eight data bits and one stop bit.
For a report of F bytes, an emitted report rate of R reports per second and a baud rate B, the calculated receive-direction utilization is U = F × R × 10 / B. This describes the module-to-host direction. It does not combine opposite UART directions or account for software processing time.
| Illustrative report rate | Report bytes per second | Wire bits per second, 8N1 | Utilization at 460800 baud |
|---|---|---|---|
| 1 kHz | 4,000 | 40,000 | 8.68% |
| 10 kHz | 40,000 | 400,000 | 86.81% |
At 10 kHz, the assumed report interval is 100 microseconds. Sending four bytes takes approximately 86.81 microseconds at 460800 baud, leaving 13.19 microseconds per interval under an evenly spaced, uninterrupted stream assumption. These are computed timing values, not measurements of LRF50H firmware. Additional bytes in the same direction, a different serial format, or a different report cadence require a fresh calculation.
The theoretical ceiling for this exact four-byte, 8N1 framing is 11,520 reports per second before any extra traffic. That arithmetic ceiling is not a supported sensor mode or a recommended operating point. A link that is nearly full leaves less room for additional output and timing variation.
Turn host pauses into a buffer budget
A receive buffer absorbs a temporary pause; it cannot correct a consumer that is permanently slower than the incoming stream. Suppose an example host allocates 2 KiB, or 2,048 bytes, of usable receive storage. This is an illustrative host allocation, not an ERDILRF module specification, driver default or hardware FIFO size.
At the assumed 10 kHz four-byte stream, an initially empty 2,048-byte buffer fills in 2048 / 40000 = 0.0512 seconds, or 51.2 ms, if the consumer stops completely. If it is already half full, the remaining 1,024 bytes cover only 25.6 ms. These figures omit extra messages and implementation overhead, so they are upper bounds for this simplified scenario, not safe timeout settings.
Use remaining time = available bytes / incoming bytes per second with the capacity and occupancy of the buffer that is actually at risk. A large application queue does not prevent a small upstream hardware FIFO from overflowing. Identify each stage: UART peripheral, interrupt or DMA transfer, driver buffer, parser and application queue. Record which stage reports loss instead of assuming every missing measurement came from the sensor.
A bench check that separates transport from ranging
- Record the configuration. Save the exact model, firmware identification if available, requested measurement mode, baud rate and framing. Obtain unresolved electrical and command details before connecting or changing settings.
- Measure the stream. Capture raw module-to-host traffic and confirm report length, interval distribution and any additional messages. Compare actual bytes received with the calculation.
- Instrument the host. Count raw bytes, accepted reports, framing or validation failures, buffer overrun events, queue occupancy and maximum time between receive-service operations.
- Introduce a controlled consumer pause. On an isolated bench setup, pause the downstream application while continuing to drain the UART. Then separately test the receive path’s service delay. Distinguish these two conditions in the log.
- Check recovery. After the pause, confirm that the parser regains alignment and the application identifies stale or missing data. A recovered connection is not evidence that every report was retained.
- Repeat under the intended workload. Include the host’s normal logging and other concurrent work. Compare the measured longest pause and highest occupancy with the project’s own acceptance limits.
Keep transport failures separate from valid out-of-range reports. For frame layout, units and the need to resolve ambiguous checksum wording, see the rangefinder serial protocol guide. Do not silently reinterpret an invalid or unavailable distance as a usable reading.
Frequently asked questions
Does 10 kHz mean my application receives 10,000 valid distances every second?
No. Measurement capability, emitted output and accepted application results are separate. Verify output behavior, signal conditions and the complete receive path for the selected mode.
Can I fix dropped data by making the buffer larger?
A larger usable buffer can cover longer temporary pauses. It cannot solve sustained overload, incorrect framing or a loss that occurs before that buffer. Measure the failing stage first.
Are the 2 KiB buffer and 51.2 ms result product specifications?
No. They are an explicit host-side example and its arithmetic result. Substitute the actual usable capacity, existing occupancy and measured incoming byte rate for your implementation.
Send ERDILRF your model, host interface and required report rate to request the current protocol details needed for a documented integration check.