BBB PractiScore Printer

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Outstanding issues

  • What to do about time/date if NTP not available (RTC on adapter card?)
  • Soft or hard power switch?
  • EEPROM for cape ID?

Controls and indicators

  • Indicators
  • Fault/OK (bi-color red/green)
  • Charging/Battery warning (bi-color red/green)
  • Switches
  • Power on/off (toggle or PB?)
  • AP/client mode select (toggle or PB?)
  • Reprint last job/print statistics (PB, short press/long press)


  • Print PractiPrint version at power on
  • Print Linux version, other useful info at power on
  • Print network status on power on or network status change
  • Print low-battery warning when battery low



  • Printer advertises self via mDNS (avahi)
  • URL request to CGI app prints information (PractiPrint)
  • Last PractiPrint output can be reprinted with reprint button
  • Status of printer (sign-on info + list of last 10 print jobs) printed with long-press of reprint button
  • Status of printer (sign-on info + all print jobs since power on) is available on root web page


  • When printer is an AP or has associated as client, fault/OK led is solid green
  • When printer is client and is associating, fault/OK led flashes yellow
  • When printer is out of paper, fault/OK light is blinks red (pattern?)
  • When printer cannot be detected by application (ESC-v), fault/OK light is solid red
  • When printer is an AP, NTP server is active
  • When printer is a client, NTP client mode is active


  • When LiFePo/SLA battery is charged, battery LED is solid green
  • When LiFePo/SLA battery is charging, battery LED blinks green (pattern?)
  • When printer is operating on battery power, battery LED is solid yellow
  • When LiFePo/SLA battery is at low voltage, battery LED blinks red (pattern?)
  • When LiFePo/SLA battery is at dead threshold, battery LED is solid red (BBB starts shutdown)

Adapter card ("cape")

  • Buck/boost power supply for input power (12V/3A)
  • LiFePo/SLA battery charging via LTC-4000
  • 9V/2A switching power supply for printer
  • 5V/2A switching power supply for BBB
  • LED drivers for fault/OK and battery LEDs (plus 2 spares)
  • Buffered input for switches (AP/client, reprint, 2 spares)
  • Serial/power connector for printer
  • Cape EEPROM (?)
  • RTC (DS3232)