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U421 PCB Pin Out
"DIP-like" Connector:
| Pin Number | U421 Signal |
| 1 | PA.0 - Port A bit 0 |
| 2 | PA.1 - Port A bit 1 |
| 3 | PA.2 - Port A bit 2 |
| 4 | PA.3 - Port A bit 3 |
| 5 | PB.0 - Port B bit 0 |
| 6 | PB.2 - Port B bit 2 |
| 7 | PB.4 - Port B bit 4 |
| 8 | PB.6 - Port B bit 6 |
| 9 | Ground |
| 10 | No Connect |
| 11 | No Connect |
| 12 | Do not use |
| 13 | No Connect |
| 14 | +5V (USB) |
| 15 | USB D- (already connected to the USB cable) |
| 16 | USB D+ (already connected to the USB cable) |
| 17 | PB.7 - Port B bit 7 |
| 18 | PB.5 - Port B bit 5 |
| 19 | PB.3 - Port B bit 3 |
| 20 | PB.1 - Port B bit 1 |
| 21 | PA.7 - Port A bit 7 (or SPI SCK) |
| 22 | PA.6 - Port A bit 6 (or SPI MISO) |
| 23 | PA.5 - Port A bit 5 (or SPI MOSI) |
| 24 | PA.4 - Port A bit 4 (or SPI SS [when in slave mode]) |
Other Connectors:
There is a 2x6 pad layout on the board used for connection to an AVR for programming. The 1x2 jumper applies 5V to this connector. The AVR programmer connector follows that of the standard 2x6 AVR programming connector. The U421-SC# (available through StrandControl) uses this connection for a way to attach 1-Wire devices.
Power Connection:
The +5V available on pin 14 is the power from the computer's USB port. Up to 100mA can be drawn from this supply to power devices attached to the U421. If more power is needed, an external supply should be used to power additional circuits. Do not attach the +5V from an external supply to this pin. The ground connection should be common to any external power supply ground as well as any target circuits.
Board Layout:
(U421-SC3 screw terminal version of the U421 available through StrandControl) Standard U421 does not have the screw terminal.
Pin 1 on the U421 is located on the lower left, as you look at the board in the orientation above. Pin 24 is the pin on the upper left. The lower row therefore is 1-12, the upper row is 24-13.
| Hardware: U401 USB Interface U421 USB Interface |
| Programming: USBm DLL Programming Download Files |
| Application Notes: U4x1 Application Notes Misc Applications and Information FAQ |