Fire Has PSRAM .. use Port C PIN ..
so it can't use Port C .

Fire 는PSRAM 이 있어요 그것이 C 포트에 GPIO를 사용합니다.
그래서 C 포트를 사용할수가 없답니다.

이 내용은 챗봇이 무척 많이 알려준 내용입니다..

https://forum.m5stack.com/topic/1930/gps-unit-at6558

@liemph Try connecting the m5stack to a pc and opening a terminal connecting to the M5Stack.
the terminal may show more information.

I took the log file by using teraterm serial monitor program. I did not see any valuable information for debugging. This is the results:
ets Jun 8 2016 00:22:57

rst:0x1 (POWERON_RESET),boot:0x17 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0018,len:4
load:0x3fff001c,len:6272
ho 0 tail 12 room 4
load:0x40078000,len:9848
ho 0 tail 12 room 4
load:0x40080400,len:6504
entry 0x4008072c
I (32) boot: ESP-IDF v3.3-beta1-696-gc4c54ce07 2nd stage bootloader
I (32) boot: compile time 19:36:27
I (32) boot: Enabling RNG early entropy source...
I (38) boot: SPI Speed : 80MHz
I (42) boot: SPI Mode : DIO
I (46) boot: SPI Flash Size : 16MB
I (50) boot: Partition Table:
I (54) boot: ## Label Usage Type ST Offset Length
I (61) boot: 0 nvs WiFi data 01 02 00009000 00006000
I (69) boot: 1 phy_init RF data 01 01 0000f000 00001000
I (76) boot: 2 factory factory app 00 00 00010000 001f0000
I (83) boot: 3 internalfs Unknown data 01 81 00200000 001ff000
I (91) boot: End of partition table
I (95) esp_image: segment 0: paddr=0x00010020 vaddr=0x3f400020 size=0xe970c (956172) map
I (379) esp_image: segment 1: paddr=0x000f9734 vaddr=0x3ffbdb60 size=0x034dc ( 13532) load
I (383) esp_image: segment 2: paddr=0x000fcc18 vaddr=0x40080000 size=0x00400 ( 1024) load
I (386) esp_image: segment 3: paddr=0x000fd020 vaddr=0x40080400 size=0x02ff0 ( 12272) load
I (398) esp_image: segment 4: paddr=0x00100018 vaddr=0x400d0018 size=0xdbea8 (900776) map
I (662) esp_image: segment 5: paddr=0x001dbec8 vaddr=0x400833f0 size=0x12bf8 ( 76792) load
I (688) esp_image: segment 6: paddr=0x001eeac8 vaddr=0x400c0000 size=0x00064 ( 100) load
I (688) esp_image: segment 7: paddr=0x001eeb34 vaddr=0x50000000 size=0x00808 ( 2056) load
I (708) boot: Loaded app from partition at offset 0x10000
I (709) boot: Disabling RNG early entropy source...
I (709) cpu_start: Pro cpu up.
I (713) cpu_start: Application information:
I (717) cpu_start: Compile time: Mar 13 2020 19:36:49
I (724) cpu_start: ELF file SHA256: 0000000000000000...
I (730) cpu_start: ESP-IDF: v3.3-beta1-696-gc4c54ce07
I (736) cpu_start: Starting app cpu, entry point is 0x400836e4
I (0) cpu_start: App cpu up.
I (746) heap_init: Initializing. RAM available for dynamic allocation:
I (753) heap_init: At 3FFAE6E0 len 0000F480 (61 KiB): DRAM
I (759) heap_init: At 3FFCB2C8 len 00014D38 (83 KiB): DRAM
I (766) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAM
I (772) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAM
I (778) heap_init: At 40095FE8 len 0000A018 (40 KiB): IRAM
I (785) cpu_start: Pro cpu start user code
I (131) cpu_start: Starting scheduler on PRO CPU.
I (0) cpu_start: Starting scheduler on APP CPU.

Internal FS (FatFS): Mounted on partition 'internalfs' [size: 2093056; Flash address: 0x200000]

Filesystem size: 2031616 B
Used: 1605632 B
Free: 425984 B

I (359) [TFTSPI]: attached display device, speed=8000000
I (359) [TFTSPI]: bus uses native pins: false
W (534) sdspi_host: spi bus changed (1 -> 2)
E (577) sdmmc_sd: sdmmc_init_spi_crc: sdmmc_send_cmd_crc_on_off returned 0x106
[ M5 ] init sd card Fail
[ M5 ] node id:<deleted>, api key:<deleted>
I (2018) uart: ALREADY NULL

Please note that I deleted the node id and api key.

@liemph do you get an error message or just no response?

Your question alerted me. I used the GPS example provided by M5 for UiFlow. The LCD showed that the Time is 00:00:00, no data in Lattitude and Longitude, the Quality showed NO Signal. I tested it at home (inside my house). So is it possible that I have to look for a better place to get a stronger signal? However other devices using GPS work well inside my house.