This device was built using USBDRV firmware developed by Objective Development.
This Low-Speed device violates following USB specification rules:
- Detachable cable (must be captive for Low-Speed)
- Output drivers with 5 V (must be 3.3 V, but USB is 5 V tolerant)
- No differential data input (only one line D- is sampled)
- No data clock regenration while receiving (only at packet start)
- No error detection of input data (OUT direction), no time for CRC16
- Data transfer using BULK pipes (not specified for low-speed, but works on Windows – for Linux there is an "Alternate Setting" with INTERRUPT pipes instead)
However, new to this firmware, following rules are accepted:
- Suspend detection and lowered suspend current (below 500 µA)
Electronic Components
You need:
| Pieces |
Description |
Reichelt Order Code |
Price in € (2007) |
| 1 |
ATmega8 in TQFP32 package
or ATmega48 |
ATMEGA 8-16 TQ
ATMEGA 48-20 AU |
1,70
1,45 |
| 1 |
Crystal 12000 kHz |
12,0000-HC49U-S |
0,24 |
| 1 |
Electrolytic capacitor 10 µF |
rad 10/35 |
0,041 |
| 1 |
USB receptacle MiniB through-hole |
USB BWM |
0,50 |
| 1 |
SubD receptacle 25 pin |
D-SUB BU 25 |
0,15 |
| 1 |
Yellow LED 3 mm |
LED 3mm ST ge |
0,051 |
| 1 |
Resistor array 220Ω |
BCN16 |
0,02 |
| 2 |
Ceramic capacitor 22 pF 0603 |
NPO-G0603 22p |
0,051 |
| 1 |
Ceramic capacitor 100 nF 0603 |
X7R-G0603 100n |
0,051 |
| 1 |
Resistor 10 kΩ 0805
or 4.7 kΩ for ATmega48 |
SMD-0805 10k
SMD-0805 4,70k |
0,10 |
| 1 |
Housing |
Kappe CG25G |
0,13 |
| 1 |
USB cable 1 m |
AK 673-A |
0,98 |
| 1 |
Two-sided PCB (see below) |
UL-15 |
5,00 |
- Detachable cable (must be captive for Low-Speed)
- Output drivers with 5 V (must be 3.3 V, but USB is 5 V tolerant)
- No differential data input (only one line D- is sampled)
- No data clock regenration while receiving (only at packet start)
- No error detection of input data (OUT direction), no time for CRC16
- Data transfer using BULK pipes (not specified for low-speed, but works on Windows – for Linux there is an "Alternate Setting" with INTERRUPT pipes instead)
However, new to this firmware, following rules are accepted:
- Suspend detection and lowered suspend current (below 500 µA)
