Use the pbm2lwxl tools. Set resolution to 300dpi.
You need to make a small modification to the USB driver. These steps were reported working.
1. Unpack linux-2.4.20
2. Change to /path/to/src/linux-2.4.20/drivers/usb
3. Edit printer.c
4. About line 880, there's the detection code. There's a check to see if the transfer type is 'bulk'. I just commented out this check. Note that according to the USB spec that I read, the 315 violates the usb LP protocol: Before:
if ((epd->bmAttributes&USB_ENDPOINT_XFERTYPE_MASK)!= USB_ENDPOINT_XFER_BULK) continue;
After:
/*if ((epd->bmAttributes&USB_ENDPOINT_XFERTYPE_MASK)!= USB_ENDPOINT_XFER_BULK) continue; */
5. Configure/compile as usual.
There are some white lines in some output. Barcodes worked fine, the text below showed some white lines. It should be fine for labels.