I partly solved the problem, with the USB-converter the ADC-101 is acting as "streaming"-device, where you have to call the "run adc100" routine before you read a block of data. My old software did not use the "run adc100" routine, as it was not necessary for the normal parallel port.
But there comes the next problem. After calling the "run adc100" routine, I check the "ready adc100" routine in a while loop, whtether the data are available for reading them with the "get block" routine. This works fine if I try to read 10 readings with 1ms intervals. But for any higher number of readings (e.g. 100 readings 1 ms, or 10 readings 10ms) the "ready adc100" routine never returns TRUE, and the program is stuck in the while loop.
Best regards, Roland