I'm trying to run one of examples delivered by Raspberry for Raspberry Pi Pico. It is an example to read data from GPS module via I2C.
Raw data from GPS should be stored in a variable char numcommand[max_read], but instead of data from GPS, there is some garbage.
Here is the full code:
/**
* Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <stdio.h>
#include <string.h>
#include "pico/stdlib.h"
#include "pico/binary_info.h"
#include "hardware/i2c.h"
#include "string.h"
/* Example code to talk to a PA1010D Mini GPS module.
This example reads the Recommended Minimum Specific GNSS Sentence, which includes basic location and time data, each second, formats and displays it.
Connections on Raspberry Pi Pico board, other boards may vary.
GPIO PICO_DEFAULT_I2C_SDA_PIN (On Pico this is 4 (physical pin 6)) -> SDA on PA1010D board
GPIO PICO_DEFAULT_I2C_SCK_PIN (On Pico this is 5 (physical pin 7)) -> SCL on PA1010D board
3.3v (physical pin 36) -> VCC on PA1010D board
GND (physical pin 38) -> GND on PA1010D board
*/
const int addr = 0x10;
const int max_read = 250;
#ifdef i2c_default
void pa1010d_write_command(const char command[], int com_length) {
// Convert character array to bytes for writing
uint8_t int_command[com_length];
for (int i = 0; i < com_length; ++i) {
int_command[i] = command[i];
i2c_write_blocking(i2c_default, addr, &int_command[i], 1, true);
}
}
void pa1010d_parse_string(char output[], char protocol[]) {
// Finds location of protocol message in output
char *com_index = strstr(output, protocol);
int p = com_index - output;
// Splits components of output sentence into array
int no_of_fields = 14;
int max_len = 15;
int n = 0;
int m = 0;
char gps_data[no_of_fields][max_len];
memset(gps_data, 0, sizeof(gps_data));
bool complete = false;
while (output[p] != '$' && n < max_len && complete == false) {
if (output[p] == ',' || output[p] == '*') {
n += 1;
m = 0;
} else {
gps_data[n][m] = output[p];
// Checks if sentence is complete
if (m < no_of_fields) {
m++;
} else {
complete = true;
}
}
p++;
}
// Displays GNRMC data
// Similarly, additional if statements can be used to add more protocols
if (strcmp(protocol, "GNRMC") == 0) {
printf("Protcol:%s\n", gps_data[0]);
printf("UTC Time: %s\n", gps_data[1]);
printf("Status: %s\n", gps_data[2][0] == 'V' ? "Data invalid. GPS fix not found." : "Data Valid");
printf("Latitude: %s\n", gps_data[3]);
printf("N/S indicator: %s\n", gps_data[4]);
printf("Longitude: %s\n", gps_data[5]);
printf("E/W indicator: %s\n", gps_data[6]);
printf("Speed over ground: %s\n", gps_data[7]);
printf("Course over ground: %s\n", gps_data[8]);
printf("Date: %c%c/%c%c/%c%c\n", gps_data[9][0], gps_data[9][1], gps_data[9][2], gps_data[9][3], gps_data[9][4],
gps_data[9][5]);
printf("Magnetic Variation: %s\n", gps_data[10]);
printf("E/W degree indicator: %s\n", gps_data[11]);
printf("Mode: %s\n", gps_data[12]);
printf("Checksum: %c%c\n", gps_data[13][0], gps_data[13][1]);
}
}
void pa1010d_read_raw(char numcommand[]) {
uint8_t buffer[max_read];
int i = 0;
bool complete = false;
i2c_read_blocking(i2c_default, addr, buffer, max_read, false);
// Convert bytes to characters
while (i < max_read && complete == false) {
numcommand[i] = buffer[i];
printf("raw data [ %d ]: %s \n", i, numcommand[i]);
// Stop converting at end of message
if (buffer[i] == 10 && buffer[i + 1] == 10) {
complete = true;
}
i++;
}
}
#endif
int main() {
stdio_init_all();
#if !defined(i2c_default) || !defined(PICO_DEFAULT_I2C_SDA_PIN) || !defined(PICO_DEFAULT_I2C_SCL_PIN)
#warning i2c/mpu6050_i2c example requires a board with I2C pins
puts("Default I2C pins were not defined");
#else
char numcommand[max_read];
// Decide which protocols you would like to retrieve data from
char init_command[] = "$PMTK314,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*29\r\n";
// This example will use I2C0 on the default SDA and SCL pins (4, 5 on a Pico)
i2c_init(i2c_default, 400 * 1000);
gpio_set_function(PICO_DEFAULT_I2C_SDA_PIN, GPIO_FUNC_I2C);
gpio_set_function(PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C);
gpio_pull_up(PICO_DEFAULT_I2C_SDA_PIN);
gpio_pull_up(PICO_DEFAULT_I2C_SCL_PIN);
// Make the I2C pins available to picotool
bi_decl(bi_2pins_with_func(PICO_DEFAULT_I2C_SDA_PIN, PICO_DEFAULT_I2C_SCL_PIN, GPIO_FUNC_I2C));
printf("Hello, PA1010D! Reading raw data from module...\n");
pa1010d_write_command(init_command, sizeof(init_command));
while (1) {
// Clear array
memset(numcommand, 0, max_read);
// Read and re-format
pa1010d_read_raw(numcommand);
pa1010d_parse_string(numcommand, "GNRMC");
// Wait for data to refresh
sleep_ms(1000);
// Clear terminal
printf("\e[1;1H\e[2J");
}
#endif
return 0;
}
And here is part of the output:
raw data [ 0 ]: 0 Raspberry Pi Trading Ltd
raw data [ 1 ]: rry Pi Trading Ltd
raw data [ 2 ]:
raw data [ 3 ]: Mu..z
raw data [ 4 ]:
raw data [ 5 ]:
raw data [ 6 ]:
raw data [ 7 ]:
raw data [ 8 ]:
raw data [ 9 ]:
raw data [ 10 ]:
raw data [ 11 ]:
raw data [ 12 ]:
raw data [ 13 ]:
raw data [ 14 ]:
raw data [ 15 ]:
raw data [ 16 ]: C.`A`pGÅT-ï..
raw data [ 17 ]: .`A`pGÅT-ï..
raw data [ 18 ]:
raw data [ 19 ]: Mu..z
raw data [ 20 ]:
raw data [ 21 ]:
raw data [ 22 ]:
raw data [ 23 ]:
raw data [ 24 ]: ) 2020 Raspberry Pi Trading Ltd
raw data [ 25 ]: ˝.L3'.T3_.MS›&S4—&MCA&C4)&UBµ%DTÖ.DEã.WV7.IF°$EXı#RE}#RP≈#FCa#CX1#ECE
Any suggestions what's wrong?
You do not check the result of the I2C read. Probably it did not read anything.
You need to know how many bytes were read or if an error has occurred:
int bytesRead = i2c_read_blocking(i2c_default, addr, buffer, max_read, false);
if(bytesRead == PICO_ERROR_GENERIC) { /* handle error */ }
else
{
/* do your stuff */
}
This is definitely wrong
if (buffer[i] == 10 && buffer[i + 1] == 10) {