Normally when you upload code to Espruino via the IDE, it is stored in Espruino's RAM. If you reset the board or power is lost, all your code will be lost.
However it's easy to save your code to flash memory and make it permanent.
On normal Espruino devices, just type save()
on the left-hand side of the IDE and the current state of
Espruino including all saved code will be written so that it is loaded at boot time.
save()
doesn't work on Bangle.js watches, since you wouldn't want to save the current state of the device
(including any Widgets/etc) into flash memory.
There are other methods of saving code that can be more efficient, or can allow you to do things like saving constants.
You can change methods using the down-arrow below the Upload icon in the IDE,
or under Communications
in the Settings
window. See below for more
information.
To understand how best to save data, it's best to know how Espruino loads saved code.
When Espruino starts up, it does a few things:
BTN1
is pressed or if it reset because of a call to reset()
, it sets hasBeenReset
to true
.hasBeenReset
wasn't set, it looks for a compressed image (.varimg
in Storage) of the interpreter's state that was saved with save()
. If it exists it unpacks it into RAM..bootPowerOn
from Storage. (On Bangle.js this is not executed if BTN1
is held down, but all other devices execute them each time).boot0
, .boot1
, .boot2
and .boot3
and executes them in sequence. (On Bangle.js these are not executed if BTN1
is held down, but all other devices execute them each time).bootrst
and executes it if it exists (see Save on Send below)If hasBeenReset
wasn't set and .bootrst
wasn't found in the last step, it looks in Storage for a file named .bootcde
and executes it (see Save on Send below)
Initialises any previously-initialised peripherals
E.on('init', function() { ... });
onInit()
if it exists.If Espruino is reset with load()
it follows the same steps as above, with hasBeenReset
to false
.
However in Espruino 2v05 and later, load(filename)
will follow the same steps but will load the
specified file instead of .bootcde
/.bootrst
.
There are two main ways to save code with Espruino:
save()
If you type save()
on the left-hand side of the IDE after your code is
uploaded, the contents of Espruino's RAM at that point will be compressed
and written in to flash memory.
This includes:
setWatch
setTimeout
and setInterval
When power is next applied, Espruino will load the information back out of flash and will resume where it left off. You can think of this a bit like 'hibernate' on a PC.
This is the standard way of saving code in normal Espruino devices (it is not suitable for Bangle.js), and it means that you can interact with your code on the left-hand side of the IDE, changing variables and functions, and can then save everything - including your changes.
For instance, if you upload the code var t = E.getTemperature()
and type
save()
, t
will contain the temperature of the device at the time that
you uploaded - not at the time the device started, or even the time you
typed save()
.
However, this means that any code that was executed at upload time will not
be re-executed. For instance you may have some external hardware like an LCD
display connected to Espruino - after applying power, the LCD will need to be
initialised (since it can not remember its state). In this case you can
create a function called onInit
(or add a E.on('init', function() { ... })
listener) that is automatically called by the interpreter when it
initialises.
Once code is saved, you can return the interpreter to a 'clean' state
with reset()
. This won't clear out any of the saved data in flash, so
if you reboot the device (or call load()
) it will re-load your previously
saved state. To completely clear out saved code, run reset()
and then
run save()
to save the clean state back into flash memory.
save()
and it will keep workingsave()
d code and can then type save()
again to save your changesE.setFlags({pretokenise:1})
will allow JavaScript code in RAM to be heavily compacted, and to execute more quickly.onInit
, or a E.on('init', function() { ... })
event handleronInit
or E.on('init', ...)
, code won't run at boot time.setWatch
and setInterval
are remembered, if you call them in onInit
and then save()
multiple times, you can end up with multiple copies. You can use clearInterval()
and clearWatch()
in onInit
to avoid that.onInit()
or E.on('init', ...)
function the function won't be called at upload time and to test you'll have to either save()
or call onInit()
manually.Save on Send
is an option in the Espruino IDE. Behind the scenes it uses
the E.setBootCode
command to save JS code directly into Espruino's
flash memory. When Espruino boots up, it then executes the JavaScript code.
This is similar to the way you'd program a 'normal' microcontroller.
For instance, if you upload the code var t = E.getTemperature()
with
Save on Send
enabled, t
will be set to the temperature every time
the device is powered on (in contrast to what happens when you use save()
.
Save on Send
(in the Communications section of the IDE) has three settings:
No
- code is uploaded to RAM, but can be saved with save()
(as above). RAM
is displayed below the upload icon.Yes
- JavaScript code is saved to flash and loaded at boot time. Flash
is displayed below the upload icon.
If reset()
is called, Espruino will remove all code from RAM and will
not execute the saved JS code. This saves your JS code
to a file in Storage called .bootcde
.Yes, execute even after reset()
- JavaScript code is saved to flash and
loaded even after boot. ⚠Flash
is displayed below the upload icon. If reset()
is called, Espruino will remove all
save()
d code from RAM, but will still execute the JS code that you saved. See
the 'Both Options' section. This saves your JS code
to a file in Storage called .bootrst
. We've now removed
this option from the Web IDE as it is dangerous and is almost certainly not what is required in 99% of cases.
If you still wish to use it, you can choose to save to Storage as .bootrst
.To remove any code saved with Save on Send
, simply call E.setBootCode()
with
no arguments.
onInit()
functionModules uploaded as functions
is enabled in the IDE.E.setFlags({pretokenise:1})
will have no effect, since a function's code will be kept in Flash (you can still add "ram"
as the first item in a function to force it to be loaded into RAM and pretokenised)Save on Send
, upload code, and then turn it off, you can be left
with both bits of code in Espruino at the same time (see 'Both Options' below).save()
after having saved to flash using a method below, you may
get Got EOF expected ..., [ERASED]
errors. These happen because there were
function definitions in RAM that referenced code in Flash that is no longer
there.This is just like Save on Send (to Flash)
, but on Espruino 2v05 and later
you may call load(filename)
to reset and load JavaScript code from a named
file stored on Espruino.
It is possible to combine Save on Send
and save()
- see Boot Process
above for more information.
This allows you to write separate code with Save on Send
that can ensure
certain things are always done, regardless of the code saved with save()
.
You can even add files called .boot0
, .boot1
, .boot2
and .boot3
to
add extra code that doesn't interfere with code saved in other ways. You
could for instance add the following code:
require("Storage").write(".boot0", `
WIFI_NAME = "MyWiFi";
WIFI_PASS = "HelloWorld123";
`);
To ensure that you always had the variables WIFI_NAME
and WIFI_PASS
defined regardless of what other code you uploaded.
For instance if you're making a device like the Espruino Home Computer
then you might want to use Save on send
or .boot0
to save all the code that initialises
the display and keyboard. The computer can then be programmed and its state
saved with save()
, but regardless of what is saved to the device you will
always be able to rely on the display and keyboard being set up correctly.
You may be able to save code to Espruino that puts it into a state that stops you from reprogramming it. On most boards, holding down a button while applying power can be used to force the device to boot without loading any of the saved code. Take a look at the information page on your specific board for more information.
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