Use a rs485 communication module

:) The custom font is slower because Espruino has to unpack it from RAM - in Espruino things sometimes aren't stored in one block of memory to work around fragmentation - so for every access it has to check.

When using the built-in font it's using very specific, fast code to access flash.

Did you try the new firmware I linked? That should be a lot faster.

Actually thinking about it, it seems that atob doesn't create a flat string when it could do.

You might get faster rendering by doing:

var font = E.toString(atob("AAAAAPoAwADAAFhw2HDQAGS­S/5JMAGCW+DzSDAxSolIMEsAAPEKBAIFCPABIMOA­wSAAQEHwQEAABBgAQEBAQAAIAAwwwwAB8ipKifAB­A/gBChoqSYgCEkrLSjAAYKEj+CADkoqKinAA8UpK­SDACAgI6wwABskpKSbABgkpKUeAAiAAEmABAoRAA­oKCgoKABEKBAAQIqQYAA8WqW9RDgOOMg4DgD+kpK­SbAB8goKCRAD+goJEOAD+kpKCAP6QkIAAfIKCklw­A/hAQEP4A/gAMAgIC/AD+EChEggD+AgICAP5AIED­+AP7AMAz+AHyCgoJ8AP6QkJBgAHyChoN8AP6QmJR­iAGSSkpJMAICA/oCAAPwCAgL8AOAYBhjgAPAOMA7­wAMYoECjGAMAgHiDAAI6SosIA/4EAwDAMAwCB/wB­AgEAAAQEBAQEBEn6SggQABCoqHgD+IiIcABwiIhQ­AHCIi/gAcKioYACB+oIAAGCUlPgD+ICAeAL4AAQG­+AP4IFCIA/AIAPiAeIB4APiAgHgAcIiIcAD8kJBg­AGCQkPwA+ECAgABIqKiQAIPwiADwCAjwAIBgGGCA­AOAYIBjgAIhQIFCIAIRkGGCAAJioyIgAQboEA5wC­BbhAAQIDAQIAAPFqlpUI8cPh8+HAAcDhwACBg/mA­gAAgM/gwIABA4fBAQABAQfDgQAHxERER8AHxE9CR­cAHxUbFR8AP58OBAAEDh8/gACAAIAAgB8fHx8fAD­+/gD+/gACilIiAgACIlKKAgA+Yu5iPgACAgICAgA­GBgYGBgAODg4ODgAeHh4eHgA+Pj4+PgB+fn5+fgD­+/v7+/gD+/v7+/gAAAAAA/gD+/gD+/v4A/v7+/gD­+/v7+/gA4OHz+/gAMDPBAIACeADhE/kQIABJ8koI­EAEQ4KDhEAKhoPmioACh8qqqCAARSqpRAAJCkqKS­QAP6CupL+ABKqqqp6ABAoVChEADh8fHw4ADhUbFQ­4AP6Cpor+ABAYHBgQAGCQkGAAIiL6IiIASJioSAC­IqKhQACBAgAB/BAQIfABgkP6A/gAwMAAAAAAASPg­IADlFRUU5AEQoVCgQAOgWKl+CAOgQKVONAKj4Bgo­fAAYJUQIADpRkFA4ADhRklA4ADlSUVA4ATpSUVI4­AjjjIOI4ADlS0VA4APkj+kpIAeISFh0gAPqpqKiI­APmqqKiIAPmqqaiIAPqoqqiIAon4iACJ+ogBivmI­AYj5iABB+UkI8AH6QiES+AByiYiIcABwiYqIcAAx­SklIMAEySklKMALxCQkK8ACIUCBQiAD5DXWE+ADy­CQgI8ADwCQoI8ABxCgkIcALwCAgK8ACAQTpAgAIH­/JSQYAH+SkmwABKpqHgAEKmqeAARqql4ARKqqXoC­EKiqeAARqql4ATFI8UjQAGCUnJAgAHKpqKhgAHCp­qmAAcaqpYAByqKpgAon4CACJ+ggBivkIAYj5CAKR­KqhoMAF6QkE6AAAySUgwADBJSjAAMUpJMAEySUow­AnCIinAAQEFQQEAA6TFRkuAAcgkIcABxCghwAHEK­CXABcAgJcADAKSoo8AIH/FQgAMIoKijwA"));
var widths = E.toString(atob("BAIEBgYGBgIEBAYGAwUCBQY­DBgYGBgYGBgYCAwQGBAUGBgYGBgUFBgYCBgYFBgY­GBgYGBgYGBgYGBgUDBQMEBgYFBQUFBQUFBQIEBQM­GBQUFBQUFBAUGBgYGBQQCBAYGBgQGBgYGBgYGBQU­GBgYGBgYGBgYGBgYGBgQCAwQFBgYGAgYGBgYGBgY­GBgYGBgYGBQYFBQQGBgMEBAYGBgYGBQYGBgYGBgY­GBgYGBgQEBAQGBgYGBgYGBgYGBgYGBgYFBQUFBQU­FBgYGBQUFBAQEBAYGBQUFBQUGBgUFBQUGBQY="))­;

  Graphics.prototype.setFontDennis8 = function() {
    this.setFontCustom(font, 32, widths, 8);
  };

So basically Dennis8, but with E.toString around atob. I'd be interested to see what difference that makes?

I'll make a note to improve atob - there's no reason it shouldn't use flat strings, which would be a lot faster and more efficient