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Supporting UART Boards - 2nd Part #47
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adam (Adam Wojcieszonek)
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Reference: adam/pyMC_Repeater#47
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An improvement suggest by ChatGpt
<html>Great — I’ll explain how to build a better UART driver layer that makes the Waveshare UART module behave much closer to a real SX1262 radio, so it works more reliably with pyMC_Repeater.
The goal is to solve the main problems:
module-added headers
missing RSSI
buffering latency
packet collisions
We do this by adding a shim layer between pyMC and the UART module.
Architecture of the improved driver
Instead of letting pyMC talk directly to the UART module:
we insert a radio shim:
The shim layer handles:
packet normalization
RSSI estimation
buffering
collision mitigation
1️⃣ Packet normalization (fix the hidden headers)
Many UART LoRa modules prepend data like:
But pyMC expects:
So we strip the header.
Example function:
Then in the RX loop:
This prevents mesh packet parsing failures.
2️⃣ RSSI estimation
Many UART modules don’t provide RSSI.
But you can estimate link quality using:
packet success rate
packet timing
retransmissions
Example:
This produces an approximate RSSI range:
Enough for routing decisions.
3️⃣ Anti-collision buffer
UART modules often transmit immediately when data arrives.
That causes collisions in mesh networks.
Add a randomized transmit delay:
This dramatically reduces collisions when several nodes repeat packets.
4️⃣ Packet queue (important)
Instead of sending directly:
use a queue system.
Example:
Start it:
This improves reliability when bursts occur.
5️⃣ Maximum payload protection
UART modules often limit payload size.
Add protection:
This prevents silent packet truncation.
6️⃣ Latency reduction trick
UART firmware buffering can add 10–80 ms delay.
You can reduce perceived latency by polling faster:
instead of:
in the RX loop.
7️⃣ Final improved pipeline
With these improvements the system behaves like:
This significantly improves mesh stability.
Typical improvements in small LoRa networks:
⚠️ One more important limitation
Even with improvements, UART LoRa modules still have a limitation:
they cannot expose the full SX1262 PHY layer.
That means you cannot control:
spreading factor
coding rate
bandwidth
precise timing
which are normally controlled over SPI.
That’s why most mesh systems (Meshtastic, pyMC, etc.) prefer SPI radios.
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