The Neo 6M GPS receiver

Most GPS receivers use a UART to communicate with their hosts and the Neo 6M is no exception. The ESP32 has 3 hardware UARTs with the following default connections:

UART number	default Rx,Tx GPIO pins
0	3,1
1	9,10
2	16,17

On our system UART 0 is reserved for REPL, GPIO 9 and 10 are not pulled out to the connector and GPIO 16,17 are used by PSRAM. Fortunately the ESP32 allows to re-map UARTs to just about any GPIO pin using the GPIO matrix and the MicroPython driver supports the re-mapping. We can define a UART as follows:

uart2=machine.UART(2, baudrate=9600, rx=21, tx=22, timeout=10000)

For more information about the ESP32 UART driver in MicroPython see

https://docs.micropython.org/en/latest/library/machine.UART.html#machine-uart

The card on which the Neo 6M GPS receiver is mounted has 4 connection pins (starting from the left):

Pin on Neo 6M	Pin on ESP32 bus
Vcc	3.3V
Rx	Rx: D1 = GPIO 22
Tx	Tx: D2 = GPIO 21, only needed if you want to modify parameters on the Neo 6M
Gnd	Gnd

Only Pin D2 or GPIO 21 is actually used and as you can tell from the instantiation of UART2 shown above the Neo 6M receiver communicates on 9600 baud.

Here is a photo of the device:

Once the connection is made and the UART instantiated all you need is an endless loop to read the UART line by line. This is what you will see if you print the result:

These are sentences of the NMEA protocol. You will need a parser that extracts the relevant information from these messages. It is not too difficult to write such a parser yourself but why do you want to do it if the job has already be done for you? In fact Peter Hinch has a github repository with gps drivers containing all you need:

https://github.com/peterhinch/micropython-async/tree/master/gps

He uses the NMEA parser from https://github.com/inmcm/micropyGPS but adapted it to his asynchronous driver.

-- Uli Raich - 2020-07-01

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