chip_test_example

Tests for LR1121 LoRa, ICM-20948 IMU, u-blox GPS on Raspberry Pi Zero W 2. Header-only drivers, kernel ioctls, no external libs.

Wiring

LR1121 (SPI0)

Module	Pi GPIO	Pi pin
SCK	GPIO11	23
MOSI	GPIO10	19
MISO	GPIO9	21
NSS	GPIO8	24
BUSY	GPIO24	18
NRESET	GPIO25	22
DIO9	GPIO4	7
DIO8	GPIO23	16

Enable: sudo raspi-config → Interfaces → SPI → Yes → reboot

ICM-20948 (I2C1)

Module	Pi GPIO	Pi pin
SDA	GPIO2	3
SCL	GPIO3	5
AD0	GND → addr 0x68 / VCC → addr 0x69

Enable: sudo raspi-config → Interfaces → I2C → Yes → reboot

u-blox GPS (UART0)

Module	Pi GPIO	Pi pin
TX	GPIO15	10
RX	GPIO14	8

Enable: sudo raspi-config → Interfaces → Serial Port → login shell: No, hardware: Yes → reboot

Build

sudo apt install g++ make
make

Run verbose first so you see exactly where it fails:

sudo ./lora_rx -v --433
sudo ./imu_test -v
./gps_test -v

LoRa debug

ls /dev/spidev0.0         # SPI on?
sudo ./lora_rx -v --433   # step labels show exactly which command hangs

If it hangs at Calibrate — that's a TCXO config issue. Try in order:

sudo ./lora_rx -v --433 --tcxo-none   # skip TCXO entirely (crystal mode)
sudo ./lora_rx -v --433 --tcxo-27     # TCXO 2.7V
sudo ./lora_rx -v --433 --tcxo-33     # TCXO 3.3V (default)

The one that gets past "Calibrate done" is your module's config. Use the same TCXO flag on TX and RX.

If using the 2.4 GHz antenna instead:

sudo ./lora_rx -v --24
sudo ./lora_tx -v --24

IMU debug

sudo i2cdetect -y 1     # 0x68 or 0x69 must show
sudo ./imu_test -v      # auto-detects both addresses
sudo ./imu_test -v -r   # raw 16-bit values

Nothing on i2cdetect: I2C not enabled, wrong wiring, or no pull-ups on SDA/SCL.

GPS debug

ls -la /dev/serial0
stty -F /dev/serial0 38400 raw && cat /dev/serial0   # raw NMEA bytes
./gps_test -v -a                                      # all sentences
./gps_test -b 9600                                    # try different baud

TCXO voltage reference

Flag	Value	Voltage
`--tcxo-none`	0xFF	no TCXO (crystal)
`--tcxo-27`	0x05	2.7V
`--tcxo-33`	0x07	3.3V
`--tcxo-v N`	0x00–0x07	raw byte

2.5 KiB Raw Blame History Unescape Escape