INTRODUCTION
FLOPPYmate requires an interface between the USB and the serial IEC bus.
The hardware described in this Blog provides an interface (SER2IEC) between UART and the serial IEC bus for peripheral devices like disk drives 1540, 1541, 1570, 1571 and 1581.
UART interface
Decide on one of these UART interface types for your FLOPPYmate:
USB to TTL adapter/bridge (Benefits: USB-powered, no Transceiver IC needed)
or
legacy RS232 (USB charger and RS232 Transceiver IC needed)
FEATURES
- No parallel port needed
- One IC (ATMEGA1284) solution
- Easy-to-build
- Handles fast data transfer (170KB disk transfer takes ca. 20s)
- Utilizes 6522 Fast Serial Driver, if installed
- Utilizes Fast Serial Mode when used with 157x and 1581 drives
LET’S GET STARTED
Schematic
Circuit Description
Direct interfacing to the IEC bus (J1) without drivers proofed to be robust enough. R1 provides Slave Select (SS) low level in SPI slave mode during fast serial byte transfer. The ATMEGA1284 was chosen because of its capability to buffer the 8KB GCR data of an entire track during a write track operation. It handles the complete IEC bus timing.