pebble/third_party/jerryscript/targets/esp8266

About

Files in this folder (embedding/esp8266) are copied from examples/project_template of esp_iot_rtos_sdk and modified for JerryScript. You can view online from this page.

How to build JerryScript for ESP8266

1. SDK

Follow this page to setup build environment

2. Patch ESP-SDK for JerryScript

Follow this page to patch for JerryScript building. Below is a summary after SDK patch is applied.

3. Building JerryScript

cd ~/harmony/jerryscript
# clean build
make -f ./targets/esp8266/Makefile.esp8266 clean
# or just normal build
make -f ./targets/esp8266/Makefile.esp8266

Output files should be placed at $BIN_PATH

4. Flashing for ESP8266 ESP-01 board (WiFi Module)

Steps are for ESP8266 ESP-01(WiFi) board. Others may vary. Refer http://www.esp8266.com/wiki/doku.php?id=esp8266-module-family page.

4.1 GPIO0 and GPIO2

Before flashing you need to follow the steps.

1. Power off ESP8266
2. Connect GPIO0 to GND and GPIO2 to VCC
3. Power on ESP8266
4. Flash

4.2 Flashing

make -f ./targets/esp8266/Makefile.esp8266 flash

Default USB device is /dev/ttyUSB0. If you have different one, give with USBDEVICE, like;

USBDEVICE=/dev/ttyUSB1 make -f ./targets/esp8266/Makefile.esp8266 flash

5. Running

1. Power off
2. Disonnect(float) both GPIO0 and GPIO2
3. Power on

Sample program here works with LED and a SW with below connection.

• Connect GPIO2 to a LED > 4K resistor > GND
• Connect GPIO0 between VCC > 4K resistor and GND

If GPIO0 is High then LED is turned on longer. If L vice versa.

6. Optimizing initial RAM usage (ESP8266 specific)

The existing open source gcc compiler with Xtensa support stores const(ants) in the same limited RAM where our code needs to run.

It is possible to force the compiler to 1)store a constant into ROM and also 2) read it from there thus saving 1.1) RAM. It will require two things though:

1. To add the attribute JERRY_CONST_DATA to your constant. For example

static const lit_magic_size_t lit_magic_string_sizes[] =

can be modified to

static const lit_magic_size_t lit_magic_string_sizes[] JERRY_CONST_DATA =

That is already done to some constants in jerry-core.

1.1) Below is a short list:

Bytes	Name
928	magic_strings$2428
610	vm_decode_table
424	unicode_letter_interv_sps
235	cbc_flags
232	lit_magic_string_sizes
212	unicode_letter_interv_len
196	unicode_non_letter_ident_
112	unicode_letter_chars

Which frees 2949 bytes in RAM.

2. To compile your code with compiler that supports the -mforce-l32 parameter. You can check if your compiler is supporting that parameter by calling:

xtensa-lx106-elf-gcc --help=target | grep mforce-l32

If the command above does not provide a result then you will need to upgrade your compiler.