/esp32_imu

9-DOF IMU using ESP32 and MPU9250

Primary LanguageCMIT LicenseMIT

ESP32 IMU

9-DOF IMU using ESP32 and MPU9250

esp32 ttgo

current status

IMU tool (May/29/2018)

One picture is worth a thousand words!

IMU tool IMU tool dashboard MAG Calibration

as of May,13,2018

CLI is implemented. Now you can access ESP32 via telnet.

By the way, the code might seem a bit intimidating at first. But that is how I think networking code should be written. Everything should be an event using an simple event loop. Otherwise you wouldn't be able to handle the complications and the concurrency in the end. Just my 10 cents on it!

telnet cli

as of May,12,2018

just getting started, folks!

Pins

Purpose Pin #
Green LED 22

Schematic

Check this out

Boot Process

To develop a firm understanding on what's going on behind the scenes, I always care about system startup process. Actually this is well explained here

To sum it up,

  1. ROM bootloader loads second-stage bootloader in SPI Flash to RAM from flash offset 0x1000

    • Second-stage bootloader source is available at components/bootloader directory of ESP-IDF.
    • Partition table is at 0x8000 of SPI flash.
    • It is interesting to note that second-stage bootloader initializes MMU!
    • Also it is interesting to note that SPI flash memory is memory mapped by MMU and can be read via normal memory read.

  2. Second-stage bootloader loads partition table and main application image

  3. main app executes

Application Memory Layout. The chip itself is not that simple. ESP32 comes with 520 KiB SRAM. Most boards I know have 4 MB SPI flash.

Type Note
IRAM instruction RAM. a part of internal SRAM0. fast execution & for ISRs
IROM instruction ROM. SPI flash.
RTC fasl for code that has to run after wake-up from deep sleep.
DRAM data ram. of course.
DROM read only data in SPI flash.
RTC slow blah blah blah

1.44 LCD

According to the shcematic, ST7735 TFT is connected to ESP32.

Name Pin #
MOSI 23
SCK 5
CS 16
MOSI 23
CMD/DATA 17
RESET N/A

One more thing to note is there is no pin to control LCD backlight with. It can be quite annoying.

Debugger Setup

  1. get openocd
  1. FTDI Connection as shown below
FT2232HL ESP32 Purpose SDIO Pin
ADBUS0 13 TCK DAT3(2)
ADBUS1 12 TDI DAT2(1)
ADBUS2 15 TDO CMD(3)
ADBUS3 14 TMS CLK(5)
GND GND GND VSS2(6)
VIO 3V3 3V3 NC

Problem is pin 12/13/14/15 are used for SDIO, which means

  • you can't use JTAG interface while using Micro-SD slot
  • we need a some special SDIO adapter to connect FT2232H and ESP32

And finally found a wonderful sdio adapter. SDIO adapter Check it out at Aliexpress

sdio adapter pin mapping 1 Left, 13 Right

SDIO Side Adapter Side Note
1 1 TDI
2 3 TCK
3 5 TDO
4 7 VDD (Do Not Connect)
5 9 TMS
6 2,4,6,8,10,12 GND
7 11 NC
8 13 NC

Got my order from China and here we go ESP32 JTAG Connect

And here we go ESP32 Openocd ESP32 GDB

esptool.py

to read parition table

esptoo.py read_flash 0x8000 0xc00 partition.img

to backup the entire flash

esptool.py read_flash 0x0000 0x400000 backup.img

to read the MAC address

esptool.py read_mac

to reset

esptool.py run

to write to flash

esptoo.py write_flash address your-bin

built-in partition table

partition table is at 0x8000 with size 0xc00

to convert binary partition table to csv

gen_esp32part.py --verify binary_partitions.bin input_partitions.csv

to convert csv to partition table

gen_esp32part.py --verify input_partitions.csv binary_partitions.bin

default esp32 partition table

Espressif ESP32 Partition Table

Name Type SubType Offset Size
nvs data nvs 0x9000 0x6000
phy_init data phy 0xf000 0x1000
factory app factory 0x10000 1M