Re: [pyusb-users] pyUSB - delayed sending to the device? / Ubuntu 19.10

[Tormod V. <lis...@gm...>]

On Tue, Mar 31, 2020 at 8:34 PM Marcin Chuć wrote:
>
> I have an ESC printer. I made a simple script to send data to the device, but after changing the content of the script - 1x the previous version of the subtitles is printed, and then, when called again, the current one. As if the data from the USB was cached somewhere. How can I make some FLUSH?
>
> usb_= Connector(showUsbDevices=False)
> usb_.send(b'I LOVE YOU')

Hi Marcin,

If you look at other code for communicating with such printers, you
will see that there is a lot of printer control codes and protocol on
top of the USB communication. With just sending these few text
characters, you are probably causing a flush of the existing buffer
and at the same time filling it up again with your new text.

See for instance this hint:
https://github.com/mike42/escpos-php/blob/development/src/Mike42/Escpos/Printer.php#L988

Regards,
Tormod