Micropython: ESP32 4MB RAM Guru Meditation Crash On Initializing UART

Created on 25 Dec 2019 · 3Comments · Source: micropython/micropython

Good Evening and Merry Christmas!

I was doing an ESP32 Micropython project that happens to use a serial port (UART 1) and decided I needed more RAM. After ordering a TTGO T8 V1.7 (ESP32, 4MB RAM, integrated MicroSD port) and setting up the most recent MicroPython build for SPI RAM, it would always reboot with a guru meditation error when I ran my code. After some poking around I found out that either declaring or initiating a UART would cause a guru meditation error and reset the ESP32. On the same board, the non-SPI RAM build does not do this. I tested this on the 3 most recent ESP32 SPIRAM builds from the download page.

Here's an example of this error on a freshly flashed copy of Micropython with nothing in boot.py:

MicroPython v1.12 on 2019-12-20; ESP32 module (spiram) with ESP32
Type "help()" for more information.
>>> from machine import UART
>>> uart = UART(1,baudrate=19200)
[0;32mI (27310) uart: ALREADY NULL[0m
>>> 
>>> 
>>> uart.init()
Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.
Core 1 register dump:
PC      : 0x400dfc04  PS      : 0x00060930  A0      : 0x800d2d91  A1      : 0x3ffc2300  
A2      : 0x3f8177c0  A3      : 0x000000b1  A4      : 0x3ffc2320  A5      : 0xffddcccc  
A6      : 0x00000001  A7      : 0x000000ff  A8      : 0x00000019  A9      : 0x3ffc22e0  
A10     : 0xffddcccc  A11     : 0x00000001  A12     : 0x00000001  A13     : 0x3ffb32c0  
A14     : 0x00000003  A15     : 0x3ffc24c0  SAR     : 0x00000000  EXCCAUSE: 0x0000001c  
EXCVADDR: 0xffddcce8  LBEG    : 0x400d2fa8  LEND    : 0x400d3000  LCOUNT  : 0x00000000  

ELF file SHA256: 0000000000000000000000000000000000000000000000000000000000000000

Backtrace: 0x400dfc04:0x3ffc2300 0x400d2d8e:0x3ffc2320 0x400f5c30:0x3ffc2360 0x400d3003:0x3ffc2380 0x400d28dd:0x3ffc23a0 0x400d67a1:0x3ffc23c0 0x40104b32:0x3ffc2440 0x40104db4:0x3ffc24e0 0x400f5b1c:0x3ffc2520 0x40092d59:0x3ffc2550

Rebooting...
ets Jun  8 2016 00:22:57

rst:0xc (SW_CPU_RESET),boot:0x13 (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:2
load:0x3fff0018,len:4
load:0x3fff001c,len:4844
load:0x40078000,len:10532
load:0x40080400,len:6736
entry 0x400806f0
[0;32mI (534) psram: This chip is ESP32-D0WD[0m
[0;32mI (534) spiram: Found 64MBit SPI RAM device[0m
[0;32mI (534) spiram: SPI RAM mode: flash 40m sram 40m[0m
[0;32mI (537) spiram: PSRAM initialized, cache is in low/high (2-core) mode.[0m
[0;32mI (544) cpu_start: Pro cpu up.[0m
[0;32mI (548) cpu_start: Application information:[0m
[0;32mI (553) cpu_start: Compile time:     Dec 20 2019 07:52:43[0m
[0;32mI (559) cpu_start: ELF file SHA256:  0000000000000000...[0m
[0;32mI (565) cpu_start: ESP-IDF:          v3.3[0m
[0;32mI (570) cpu_start: Starting app cpu, entry point is 0x40083d90[0m
[0;32mI (562) cpu_start: App cpu up.[0m
[0;32mI (1446) spiram: SPI SRAM memory test OK[0m
[0;32mI (1446) heap_init: Initializing. RAM available for dynamic allocation:[0m
[0;32mI (1446) heap_init: At 3FFAE6E0 len 00001920 (6 KiB): DRAM[0m
[0;32mI (1453) heap_init: At 3FFBA658 len 000259A8 (150 KiB): DRAM[0m
[0;32mI (1459) heap_init: At 3FFE0440 len 00003AE0 (14 KiB): D/IRAM[0m
[0;32mI (1465) heap_init: At 3FFE4350 len 0001BCB0 (111 KiB): D/IRAM[0m
[0;32mI (1472) heap_init: At 400973F0 len 00008C10 (35 KiB): IRAM[0m
[0;32mI (1478) cpu_start: Pro cpu start user code[0m
[0;32mI (155) cpu_start: Chip Revision: 1[0m
[0;33mW (155) cpu_start: Chip revision is higher than the one configured in menuconfig. Suggest to upgrade it.[0m
[0;32mI (158) cpu_start: Starting scheduler on PRO CPU.[0m
[0;32mI (0) cpu_start: Starting scheduler on APP CPU.[0m
MicroPython v1.12 on 2019-12-20; ESP32 module (spiram) with ESP32
Type "help()" for more information.
>>> 
>>> 
>>>

Apologies for odd formatting, that was copied straight from upycraft and it handles characters a bit weirdly.

Source

Trekintosh

Most helpful comment

The default pin assignments for UART 1 collide with the GPIO pins of the RAM. When instantiating UART, you have to specify other pins for tx and rx, like 4 and 5.

robert-hh on 25 Dec 2019

👍2

All 3 comments

The default pin assignments for UART 1 collide with the GPIO pins of the RAM. When instantiating UART, you have to specify other pins for tx and rx, like 4 and 5.

robert-hh on 25 Dec 2019

👍2

The default pin assignments for UART 1 collide with the GPIO pins of the RAM. When instantiating UART, you have to specify other pins for tx and rx, like 4 and 5.

Thanks! That was the issue, and I feel like a doofus. In my project I changed tx and rx when I initialized the chatpad, but not when I instantiated it, which is when it was actually crashing for me. Working good now!

Trekintosh on 25 Dec 2019

Since this is a known trap, it should have been changed since long.

robert-hh on 25 Dec 2019

👍1

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