uart transmission

[mauroForlimpopoli]

Good afternoon,
i'm using uart with this code:

let serial17 = new device.io.Serial({
		receive: 2,
		transmit: 3,
		baud: 9600,
		port: 1,
		format: "buffer",
		onReadable: function(count) {
// other code
	});	 

and I send periodically (every 10 sec.) with che instruction

serial17.write(ArrayBuffer.fromString("sting fo about 40 just for example hallo world"))

and all words, and on my app "teraTerm" appears

sting fo about 40 just for example hallo world
sting fo about 40 just for example hallo world

but sometimes the synco is lost and it trasmits:

hallo world
sting fo about 40 just for example hallo world
hallo world

I think maybe the example is not clear, but in other words the buffer transmitted is:

example hallo world
sting fo about 40 just for 

It is like if the part of the previus buffer is not transimitted and with the next transmission it finish the first and transmit a part of the new one.
It is possible or my error? Can I reset the buffer not trasmitted to syncronize it?
It seems that the problem is at the first start
Thank you

[phoddie]

The message being transmitted is short enough that it fits into the ESP22 hardware UART FIFO. That's going to be transmitted in one continuous burst.

From your first example, it seems like the start of the message is sometimes being lost. That can happen after a long pause in transmission, while the receiver re-syncs with the transmitted If you reduce the interval to 1 second, does that change the behavior?.

[mauroForlimpopoli]

Good afternoon Peter, in these days I did some test but no error from the UART with 1 sec. of transmission and with 10 sec. too. I will try again Anyway, there is a way to reset the Buffer of the UART? Mauro Lorenzi

…

Il 12/10/2025 00:42 CEST Peter Hoddie ***@***.***> ha scritto: phoddie left a comment (Moddable-OpenSource/moddable#1538) #1538 (comment) The message being transmitted is short enough that it fits into the ESP22 hardware UART FIFO. That's going to be transmitted in one continuous burst. From your first example, it seems like the start of the message is sometimes being lost. That can happen after a long pause in transmission, while the receiver re-syncs with the transmitted If you reduce the interval to 1 second, does that change the behavior?. — Reply to this email directly, view it on GitHub #1538 (comment), or unsubscribe https://github.com/notifications/unsubscribe-auth/ASV75YZXSA56V7ZC2DI7WZD3XGBUJAVCNFSM6AAAAACI3J2YJWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTGOJTG4YTCNZWGY. You are receiving this because you authored the thread.Message ID: ***@***.***>

[phoddie]

in these days I did some test but no error from the UART with 1 sec. of transmission and with 10 sec. too. I will try again

Good. So it seems like the receiver needs to see signals on the line more often or it can take a while to resync, causing some lost data. If you don't want to send all the data every second, you could send some dummy data (nulls) at regular intervals between your main transmission, or you could repeat some leading character (space or null) several times before you start your transmission.

Anyway, there is a way to reset the Buffer of the UART?

Not at present. But that's not going to help here, at least not in anyway I can see.

[mauroForlimpopoli]

This is the code
serTUG(Uint8Array.of(0x61,0x06,0x00,0x36,0x00,0x00,0x60,0x64)); // start
function serTUG (txt) { trace(txt, " tug\n") serial17.write(txt.buffer); }

video_20251028_171908-c.mp4

the text in trace is correct, but in the "RS232 analizer" some characters are sent later
This happens whether I transmit to the connected sensor or just transmit "RS232 Analizer"

[phoddie]

That's a code fragment. Here's a full working example of what I understand you are trying to do:

import Timer from "timer";

const uart = new device.io.Serial({
	...device.Serial.default,
	baud: 9600,
});


let counter = 0;
Timer.set(() => {
	uart.write(ArrayBuffer.fromString(`Test string ${++counter}\r\n`));
}, 0, 10_000)

This works as expected running on Moddable Six over the default serial port connected to a Mac. The strings are delivered every 10 seconds, with no delay and no dropped characters.

[mauroForlimpopoli]

Good morning Peter, sorry for my late answer.
My idea was a bit different, but I tried you solution
this is the code:

function serOut () {

	Timer.set(() => {
		if(stringToSend2 != "" && stringToSend2 != undefined ) {
			trace(stringToSend2, " stringToSend2TX\n")	
			serial17.write(ArrayBuffer.fromString(stringToSend2));
			stringToSend2 = ""
		}
	}, 0, 15_000)
}

and this the out:

###,02 Dic 2025 10:46,25Nov25161824,------------------------,------------------------,2,0, --- , --- ,no,no,0,0,0,0,RAMSTORE,ORANGE,1.1.15Z,-,30000000,no,8634,
 stringToSend2TX
C:\Users\mades\Projects\moddable\modules\io\serial\esp32\serial.c (352) # Break: output full (in write)!

with shorter string it works

[mauroForlimpopoli]

let aa = 0
let bufSerial = stringToSend2.slice(aa,(aa+5))
while(bufSerial != "" ){	
	serial17.write(ArrayBuffer.fromString(bufSerial))
	Timer.delay(Preference.get("speedSet", "integer"));
	aa = aa +5
	bufSerial = stringToSend2.slice(aa,(aa+5))
}

At the moment I add a split of string and a delay or 30 mSec.
It seems work
I wiil see in next days

[phoddie]

Please properly format your reports. It is not reasonable to expect others to edit them to be readable. You may find the GitHub guide to Creating and highlighting code blocks relevant. The Preview feature in the GitHub editor may be used to confirm that your formatting is applied you expect.

Regarding the "output full" exception, the serial input and output have a buffer of finite size. The ESP32 hardware buffers are 128 bytes each. Use the onWritable callback to know when there is buffer space available to write and how large a write will be accepted. See serial/continuouswrite for an example.

[mauroForlimpopoli]

Good morning Peter, sorry for formatting, but I always did that.
Coming to uart transmission, maybe I understud that the problem is caused from the delay between the 2 parts of the string I send because is longer than 128 byte.
So I reduce the value to 1 ms and it looks works good.
This solultion is not very nice because I use

serial17.write(ArrayBuffer.fromString(bufSerial))

without to use onWritable: function().

This is my serial port:

	serial17 = new device.io.Serial({
		receive: 2,
		transmit: 3,
		baud: baud,
		port: port,
		format: type,
		onReadable: function(count) {
                      ......................  // code
              	}
	});

In my proget "bufSerial" can be longer than 128 byte, so how can I do send a long string and use "onWritable" like flow control ? I mean my delay is always "fixed" from a timer that can be too long and too short
I don't know if the question in clear
Thank you

[phoddie]

sorry for formatting, but I always did that

We can all learn and improve. Please do try. I even took the time to share links to help.

Perhaps the class at the end of this chat does what you want?

https://claude.ai/share/cb251fa1-963c-4053-aad5-e0d883110db4