there, just create a new GPS object and start feeding it data using the ```update()``` method. After you've feed it an entire valid sentence, it will return the sentence type and the internal GPS attributes will be updated. The example below shows the parsing of an RMC sentence and the object returns a tuple with the current latitude data
The object will continue to accept new characters and parse sentences for as long as it exists. Each type of sentence parsed can update different internal attributes in your GPS object.
If you have `pytest` installed, running it with the ```test_micropyGPS.py``` script will parse a number of example sentences of various types and test the various parsing, logging, and printing mechanics.
Data successfully parsed from valid sentences is stored in easily accessible object variables. Data with multiple components (like latitude and longitude) is stored in tuples.
Current speed is stored in a tuple of values representing knots, miles per hours and kilometers per hour
```sh
>>> my_gps.speed
(5.5, 6.3305, 10.186)
```
### Time and Date
The current UTC time is stored (hours,minutes,seconds)
```sh
>>> my_gps.timestamp
(8, 18, 36.0)
>>> my_gps.date
(22, 9, 05)
```
The timezone can be automatically adjusted for using the by setting the ```local_offset``` when you create the object or anytime after. Setting it to ```-5``` means you are on Eastern Standard time in the United States.
```sh
>>> my_gps = MicropyGPS(-5)
>>> my_gps.local_offset
-5
# Update With Timestamp Sentence Data...
>>> my_gps.timestamp
(3, 18, 36.0)
```
The current UTC date is stored (day,month,year). **NOTE:** The date is not currently adjusted to match the timezone set in ```local_offset```.
```sh
>>> my_gps.date
(22, 9, 05)
```
### Satellite Data
Signal quality and individual satellite information is collected from GSV, GSA, and GGA sentences and made available in the following variables.
```sh
>>> my_gps.satellites_in_use
7
>>> my_gps.satellites_used
[7, 2, 26, 27, 9, 4, 15]
# Fix types can be: 1 = no fix, 2 = 2D fix, 3 = 3D fix
>>> my_gps.fix_type
3
# Dilution of Precision (DOP) values close to 1.0 indicate excellent quality position data
>>> my_gps.hdop
1.0
>>> my_gps.vdop
1.5
>>> my_gps.pdop
1.8
```
The ```satellite_data_updated()``` method should be check to be ```True``` before trying to read out individual satellite data. This ensures all related GSV sentences are parsed and satellite info is complete
```sh
>>> my_gps.satellite_data_updated()
True
# Satellite data is a dict where the key is the satellite number and the value pair is a tuple containing (Elevation, Azimuth, SNR (if available))
While parsing sentences, the MicropyGPS object tracks the number of number of parsed sentences as well as the number of CRC failures. ```parsed_sentences``` are those sentences that passed the base sentence catcher with clean CRCs. ```clean_sentences``` refers to the number of sentences parsed by their specific function successfully.
```sh
>>> my_gps.parsed_sentences
14
>>> my_gps.clean_sentences
14
>>> my_gps.crc_fails
0
```
The amount of real time passed since the last sentence with valid fix data was parse is also made available. **NOTE:** On the pyBoard, this value is returned in milliseconds while on Unix/Windows it is returned in seconds.
micropyGPS currently can do very basic automatic logging of raw NMEA sentence data to a file. Any valid ASCII character passed into the parser, while the logging is enabled, is logged to a target file. This is useful if processing GPS sentences, but want to save the collected data for archive or further analysis. Due to the relative size of the log files, it's highly recommended to use an SD card as your storage medium as opposed to the emulated memory on the STM32 micro. All logging methods return a boolean if the operation succeeded or not.
```sh
# Logging can be started at any time with the start_logging()
>>> my_gps.start_logging('log.txt')
True
# Arbitrary strings can be written into the log file with write_log() method
>>> my_gps.write_log('Some note for the log file')
True
# Stop logging and close the log file with stop_logging()
Several functions are included that allow for GPS data to be expressed in nicer formats than tuples and ints.
```sh
>>> my_gps.latitude_string()
"41° 24.8963' N"
>>> my_gps.longitude_string()
"81° 51.6838' W"
>>> my_gps.speed_string('kph')
'10.186 km/h'
>>> my_gps.speed_string('mph')
'6.3305 mph'
my_gps.speed_string('knot')
'5.5 knots'
# Nearest compass point based on current course
my_gps.compass_direction()
'NE'
>>> my_gps.date_string('long')
'September 13th, 2098'
# Note the correct century should be provided for GPS data taken in the 1900s
>>> my_gps.date_string('long','19')
'September 13th, 1998'
>>> my_gps.date_string('s_mdy')
'09/13/98'
>>> my_gps.date_string('s_dmy')
'13/09/98'
```
## Pyboard Usage
Test scripts are included to help get started with using micropyGPS on the [pyboard] platform. These scripts can be copied over to the pyboards internal memory or placed on the SD Card. Make sure, when running them on the pyboard, to rename script you're using to **main.py** or update **boot.py** with the name of script you wish to run.
- **uart_test.py** is a simple UART echo program to test if both your GPS is hooked up and UART is configured correctly. Some of the standard NMEA sentences should print out once a second (or faster depending on your GPS update rate) if everything is OK
- **sentence_test.py** will try and parse all incoming characters from the UART. This script requires micropyGPS.py be present in the same area of storage (SD Card or internal). Whenever a set of characters comprising a valid sentence is received and parsed, the script will print the type of sentence.
- **GPIO_interrupt_updater.py** is an example of how to use external interrupt to trigger an update of GPS data. In this case, a periodic signal (1Hz GPS output) is attached to pin X8 causing a mass parsing event every second.
An example of how to hookup the pyboard to the Adafruit [Ultimate GPS Breakout] (minus the PPS signal needed in the external interrupt example) is shown below.
You can follow the setup instructions for the pyboard. The only difference is, that you shoud use micropyGPS as a [frozen module]. Otherwise there will be exceptions, because there is not enough heap space available.
As mentioned above, micropyGPS also runs on Python3.x (that's where most of the development was done!). This is useful for testing code or just parsing existing log files.
Beyond the pyBoard and ESP32, micropyGPS should run on other embedded platforms that have an Python3 interpreter such as the Raspberry Pi and BeagleBone boards. These other devices are currently untested.
