HP 75 and the PIL-Box

[J-F Garnier]

The main limitation comes from the FTDI driver, so it is very important to reduce the lantency timer to a minimum (1ms) as pointed out by Sylvain.

The second limitation is the serial speed between USB and the PIL-Box uC, using the 115kps setting makes it negligible.

With these settings, transfer rate will be in the range of 200-400 bytes/s. Still lower than the real HP hardware and more than enough for the HP-41, but the limited transfer rate is noticeable with the HP71B/HP75.

My today's tests with 1 ms timer latency and 115kps PIL-Box settings, using a HP-71B and a 1722 byte test file, show that the transfer rate also depends on the host system:

My old Win2K desktop - FTDI 2.08.02 : 9.8s (175 bytes/s)

My latest Win8-64bit notebook - FTDI 2.08.30 : 3.8s (450 bytes/s)

J-F

(to measure transfer rate, I use something like: T=TIME @ COPY xxx TO :2 @ DISP TIME-T)

Added: with scope trace disabled in ILPer...