LB-68B50-01

Features

• Serial/Parallel I/O Card
• 68B50 UART
• 1.8432 MHz oscillator
  • Baud Rate Clock (38.4k baud oscillator)
• XIAO RP2040 CPU
  • USB/Serial
• 8-bit parallel port expander
• SD card
• 100x50mm card

Design

ACIA -Rev 2

• 68B50 UART
• Baud Rate Clock (38.4k baud oscillator)

ACIA -Rev 1

• 68B50 UART
• Baud Rate Clock (38.4k baud oscillator)

XIAO RP2040 CPU - Rev 2

• Fix 3.3V levels

• USB/Serial
• Drive SPI I2C 8-bit parallel port expander
• SD card

J4 - FTDI Header (Rev 2)

• 5V levels
• Pinout

1. GND
2. CTS (in)
3. VCC
4. TX (out)
5. RX (in)
6. RTS (out)

XIAO RP2040 CPU - Rev 1

• Fatal flaw, can't use the RP2040 since the UART voltages are 5V and the RP2040 doesn't work at 5V

• USB/Serial
• Drive SPI I2C 8-bit parallel port expander
• SD card

Parallel I/O Port

• 3.3V levels
• I2C Bus driven from RP2040
• Int to RP2040

SD Card (Rev 2)

• Connected to RP2040
• Can be used to send program code to the CPU

SD Card (Rev1)

• Need to not install level translators
• Need to short across the SD card lines

Backplane

Mechanicals

Rev 2

• Move J3 GND, VCC silkscreen over

Rev 1

Checkout

Rev 2

• Removed U2 voltage translator connections to SD Card and connect to serial lines between 5V ACIA and 3.3V RP2040
• Lift pin U1-8
• Lift pin U1-10
• Connect U1-8 to U1-10 to Vcc
• Add FTDI connector

Rev 1

• Do not install level translator U3
• Short across the SD card lines
  • Jumper U2-13 to U2-2
  • Jumper U2-12 to U2-3
  • Jumper U2-11 to U2-4
  • Jumper U2-10 to U2-5
• Cut etch U1-8
• Cut etch U1-10
• Add jumper U1-8 to U1-10 to U1-12
• Cut etch U1-14 (E pin of ACIA)
• Add jumper U1-14 to J1-49 (VDA)

Assembly Sheet

• Interactive BOM