PCB overview
Antenna connectors – There are two uFL antenna connectors, one for LTE-M and other other for a GPS antenna
QWIIC connector – The PCB is loaded with a QWIIC which allows for the easy addition of compatible I2C devices to the Raspberry Pi.
I2C pins – 3.3v, GND and the I2C pins from the Raspberry Pi are broken out on the left side of the PCB.
Gyro & Accel SPI pins – These are the SPI pins for the gyroscope and accelerometer. By default, the sensors are connected via I2C. If you would like to use SPI for these sensors, you need to first break the I2C connection, cut the traces on the I2C BEAK jumpers shown below, this will break the I2C connection between the gyro accelerometer. This place a solder blob on JP9 to complete the SPI connection.
Disable Power LED – If you whish to disable the power led, cut the trace in jumper LED. To re-enable, please a solder blob on the jumper to close the connection.
LTE-M related information
Power pin – The pin labelled PWR on the bottom left side can be used to wake the LTE-M modem.
Reset pin – The pine labelled RSTN will reset the LTE-M module and used in combination with the power pin can shutdown the LTE-M modem. See the datasheet for more information.
Time Pulse – The pin labelled TP is for time pulse output.
Input triggered interrupt – The pin labelled INT is time stamp of external interrupt input. Currently not on this version of SARA-R5
LEDs
PWR LED – Indicates power to the PCB
LED 1 and LED2 are connected to the GPIO of the SARA-R5 module, these GPIO can be enabled to support different functions, such as;
+Input
+Output
+Network status (Default configuration for LED2)
+Module status
SIM card detection
+Ring Indicator
See the datasheet for the complete list.
LED1 – Unconfigured. Connected to GPIO1(pin16) on SARA-R5
LED2 – Connected to GPIO5(pin19) on SARA-R5. By default, this is configured with the status of the provider .
A simple example of how to set GPIO5 to output and then set it to high, which will turn LED2 on.
Connect to the console on the SARA-R5, using minicom;
The first AT command below will change the mode of the GPIO pin, ‘0’ is to set the pin for output
The second command is to write a ‘1’ to this pin which will set it high
AT+UGPIOW=19,1
You can use AT+UGPIOC? to get the current state of all GPIO
+UGPIOC:
16,2
19,0
23,255
24,255
25,255
33,255
42,255
46,255
OK
Assemble PCB
OzzMaker SARA-R5 LTE-M GPS + 10DOF comes with one 5×2 female header.
This header needs to be soldered onto the back of the PCB. The image below shows where it is placed;
Accessing LTE-M console
By default, only one UART channel is enabled on the OzzMaker SARA-R5 LTE-M module.
Accessing the module in the default config will only give you access to the LTE-M module. You can still access GPS data, however it will need to be done using AT commands.
Access default UART channel;
pi@raspberrypi ~ $ minicom -b 115200 -o -D /dev/serial0
When enabling the multiplexer protocol on the Raspberry Pi and SARA-R5 module, you can access 4 UART channels which would be able to perform these functions;
- Channel 0 – Control Channel
- Channel 1 – AT Commands and Data
- Channel 2 – AT Commands and Data
- Channel 3 – GNSS Streaming
This would allow you to have a data connection, perform AT commands and stream GPS NMEA sentences all at the same time.
You can follow this guide on how to enable the multiplexer protocol,
IMU
- 0x6A for the gyroscope and accelerometer
- 0x30 for the magnetometer
- 0x77 for the pressure sensor
Gyroscope and accelerometer I2C address – JP8 – By default, this jumper is open, which gives the gyroscope and accelerometer an address of 0x6A. When closed, the address will change to 0x6B. The jumper can be closed by placing a blob of solder on the jumper
Pressure senor I2C address – JP4 – By default, this jumper is closed, which gives the pressure sensor an I2C address of 0x77. Opening this jumper will change the I2C address to 0x76. This can be opened by cutting the trace in between the jumper pads with a knife.
IMU Code
Git repository here
The code can be pulled down to your Raspberry Pi with;
Schematic
