Print on a BLE printer

[mauroForlimpopoli]

Good evening,
I'm trying to print on a BLE printer.
I'm using the example "https://github.com/Moddable-OpenSource/moddable/blob/public/examples/network/ble/uart-client/main.js"
The connection and "onServices" event are done, but no "onCharacteristics(" event is received.
I tried to change "service" and "characteristics" UUID, with
"
const SERVICE_UUID = uuid38eb4a80-c570-11e3-9507-0002a5d5c51b;
const CHARACTERISTIC_RX_UUID = uuid38eb4a81-c570-11e3-9507-0002a5d5c51b;
const CHARACTERISTIC_TX_UUID = uuid38eb4a82-c570-11e3-9507-0002a5d5c51b;
"
but it doesn't work.
What can I do?
regards

[mauroForlimpopoli]

...the printer has a POS/ESC command

[mauroForlimpopoli]

..partial correction...
I receive the onServices" event but the array is empty.
I found some example on the web and it seems that it simplest than I expect. It could be enough to send a text string with ESC/POS command after the connection to set and print data. Is it possible, how can I do that ?
Regards

[mauroForlimpopoli]

when I try to write to a server I always get this error.

In the array which Arg is wrong?

[phoddie]

The second argument must be an ArrayBuffer. You are passing a string. Use ArrayBuffer.fromString() to convert the string to an ArrayBuffer before making the call.

[mauroForlimpopoli]

I done the correction and now it works !!!
Thank you very much !

[phoddie]

@mauroForlimpopoli - I'm curious. Were you able to get your BLE printer working?

[mauroForlimpopoli]

Yes !!!
for first I found the "name" of the printer (it was "Printer Bluetooth")
then this is shorty my code:

	const SERVICE_UUID = uuid`00001800-0000-1000-8000-00805f9b34fb`;
	const CHARACTERISTIC_RX_UUID = uuid`49535343-1E4D-4BD9-BA61-23C647249616`;
	const CHARACTERISTIC_TX_UUID = uuid`49535343-8841-43F4-A8D4-ECBE34729BB3`;

This is the main step for the connection

		onServices(services) {	
			services.forEach(service => {
				let uuids = service.uuid;
			});		
			if (services.length)
				services[3].discoverAllCharacteristics();
		}

Of course I use the printer only using the POS standard protocol