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Hardware Compatibility

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Is this bug report about any UI (https://meshtastic.org/docs/configuration/device-uis/) component firmware?

• Meshtastic UI aka MUI
• InkHUD
• BaseUI

Firmware Version

2.7.23 alpha

Description

Title:
M5Stack Unit-C6L: SX_LNA_EN / PI4IO P5 may not be enabled, weak RX / no distant nodes

Body:
Hello,

I am testing the M5Stack Unit-C6L with Meshtastic and I may have found a possible RX path / LNA initialization issue.

Hardware:

• M5Stack Unit-C6L

Firmware:

• Target: m5stack-unitc6l
• Firmware: Meshtastic 2.7.23 alpha
• Region: EU_868
• Tested presets: LongFast and ShortSlow
• Frequency shown in log: 869.525 MHz

Problem:
Two identical Unit-C6L devices can communicate with each other at short distance, so the SX1262 radio is not completely dead.

However, the device does not seem to receive any local/distant Meshtastic nodes. With EU_868 / ShortSlow I still see:

num_packets_rx=0
num_packets_rx_bad=0
channel_utilization=0.000000
num_total_nodes=1

Radio init looks successful:

Set radio: region=EU_868, name=ShortSlow, config=5, ch=0, power=27
frequency: 869.525024
SX1262 init success
Set RX gain to boosted mode; result: 0

Possible cause:
According to the M5Stack Unit-C6L documentation, the PI4IOE5V6408 controls:

E0.P5 = SX_LNA_EN
E0.P6 = SX_ANT_SW
E0.P7 = SX_NRST

The documentation says LoRa initialization requires:

SX_NRST high
SX_ANT_SW high
SX_LNA_EN high

In the M5Stack Arduino example, all three pins are set high:

ioe.digitalWrite(7, true); // SX_NRST
ioe.digitalWrite(6, true); // SX_ANT_SW
ioe.digitalWrite(5, true); // SX_LNA_EN

But in the Meshtastic m5stack_unitc6l variant code, it looks like only P7 and P6 are configured/set:

// P7 LoRa Reset
// P6 RF Switch
// P5 LNA Enable

i2c_write_byte(... PI4IO_REG_IO_DIR, 0b11000000);
i2c_write_byte(... PI4IO_REG_OUT_SET, 0b10000000);

setbit(in_data, 6);
i2c_write_byte(... PI4IO_REG_OUT_SET, in_data);

I do not see P5 / SX_LNA_EN being configured as output or set high.

Expected behavior:
If SX_LNA_EN is required for proper RX performance, PI4IO P5 should probably be configured as output and set high during Unit-C6L LoRa initialization.

Possibly something like:

i2c_write_byte(... PI4IO_REG_IO_DIR, 0b11100000);
setbit(in_data, 5); // SX_LNA_EN HIGH
setbit(in_data, 6); // SX_ANT_SW HIGH

Question:
Can someone confirm whether SX_LNA_EN / PI4IO P5 should be enabled in the Meshtastic Unit-C6L variant?

This may explain why short-range communication between two nearby Unit-C6L devices works, but distant/local nodes are not received.

Additional notes:

• The device was flashed with Full Erase and Install.
• EU_868 is correctly set after configuration.
• The radio initializes successfully.

Relevant log output