Module sx1302 

Semtech SX1302 and SX1303 concentrators.

A transceiver listens to one channel at a time. A concentrator listens to eight at once, across every spreading factor, which is what separates a gateway from a node. That is also why it is driven differently: the SX126x and SX127x take commands, while this chip is a map of registers, most of them a few bits inside a byte shared with their neighbors.

Nothing works until two microcontrollers inside the chip are given firmware. The gain control one sets the front end, the arbiter shares the radios between the receivers, and both come up empty, so a concentrator that has been powered but not loaded reports a healthy version register and hears nothing at all.

This module carries that as data:

• spi - the transfers the chip answers, byte for byte, and how a long write is split.
• register - where the blocks are and which bits inside a byte each register owns.
• chip - the version that says a board is answering, and the part number that says whether it is an SX1302 or an SX1303.
• channel - the frequencies the receivers listen on, the spreading factors they look for, and the order all of that is set in.
• firmware - the order the two microcontrollers are loaded in, and what to check afterwards.
• mcu - configuring those two microcontrollers once they are loaded, which is the other half of bringing one up.
• rx - the packets the receive buffer holds, and what the receiver made of each.
• tx - where a payload is written, how far ahead of its window a send starts, and the three ways a transmission is triggered.
• lbt - the commands for the SX1261 beside the concentrator, which listens to a channel before the gateway is allowed to talk on it.
• sx1261 - bringing that radio up, which has to happen before those commands mean anything to it.
• sx1250 - the front ends the concentrator listens through, which are what a carrier is tuned to, and the order one is brought up in.
• timestamp - the counter packets are stamped against and receive windows are measured from, and how it is widened past a rollover.
• bridge - the messages that carry all of the above through the microcontroller on a USB card, which does the SPI on the host’s behalf.

With the embedded-hal feature, the Sx1302 driver walks all of that against a real bus: it resets the board, reads the version, resets the front ends, and gives each microcontroller its firmware.

None of it opens a bus, so a frame can be checked against the reference implementation, or against a capture from a working gateway, with no hardware present.

The register map, the transfer framing, and the load sequence follow Semtech’s sx1302_hal, which is BSD 3-Clause. The notice is on the notices page.

Examples

Asking a board what it is, without a bus in sight.

use pamoja_radios::sx1302::{chip, register, spi};

// The version register is read like any other: the target, the register's address
// most significant byte first, a dummy byte, and the byte the chip answers in.
let version = register::COMMON_VERSION.address;
let [high, low] = version.to_be_bytes();
let asked = spi::read(spi::TARGET_CONCENTRATOR, version);
assert_eq!(asked, [spi::TARGET_CONCENTRATOR, high, low, 0, 0]);

// A concentrator that is powered and wired the right way round answers with one value.
assert!(chip::answers(0x10));
assert!(!chip::answers(0x00));

// The part number takes two transfers, because it lives in one-time programmable memory.
let [select, read] = chip::identify();
assert_eq!(select, chip::Step::Write(register::OTP_BYTE_ADDR, 0xd0));
assert_eq!(read, chip::Step::Read(register::OTP_RD_DATA));

assert_eq!(chip::Model::of(0x03), chip::Model::Sx1303);

Modules

bridge

Reaching a concentrator through the microcontroller on a USB card.

channel

Pointing a concentrator at the channels it listens on.

chip

Telling the concentrator apart from its relatives, and from nothing at all.

firmware

Putting firmware into the two microcontrollers the concentrator runs.

lbt

Listening before talking, on the SX1261 beside the concentrator.

mcu

Starting the two microcontrollers inside a concentrator.

register

Where the concentrator keeps its registers.

rx

Reading packets out of the concentrator.

spi

The SPI transactions the SX1302 answers.

sx1250

The SX1250 front ends a concentrator listens through.

sx1261

Bringing up the SX1261 that listens beside the concentrator.

timestamp

The counter a concentrator stamps packets against.

tx

Putting a packet on the air.

usb

A concentrator on a USB card, driven through its bridge.

Structs

Sx1261

The SX1261 beside a concentrator, on its own SPI device with its reset line.

Sx1302

A concentrator on an SPI device, with its reset line.

Enums

ConcentratorError

Why the concentrator could not be driven.

ListenerError

Why the listening radio could not be driven.

Constants

ABORT_POLLS

How many one-millisecond polls an aborted chain is given to come free: the second Semtech’s sx1302_tx_abort waits.

COMMAND_WAIT_US

How long every command waits before it goes out, in microseconds, in place of the BUSY pin no concentrator card wires.

LISTENER_RESET_US

How long the reset line is held low, and then how long the radio is given after it, in microseconds: the tenth of a second Semtech’s reset_lgw.sh waits after every edge.

RADIO_CALIBRATE_US

How long an SX1250 is given to finish calibrating itself, in microseconds.

RADIO_RESET_HOLD_US

How long a front end is held in reset, in microseconds, as the reference holds it.

RADIO_RESET_SETTLE_US

How long a front end is given to come out of reset, in microseconds.

RESET_HOLD_US

How long the reset line is held, in microseconds.