I like things small and powerful. I decided to extend ATS-3A abilities to send digital modes. For this extension I needed a programmer for the MPS430 microcontrollers. Olimex sells a cheap simple parallel JTAG programmer . The schematic is exact copy of the MSP430 Parallel Port Debugging Interface MSP-FET430PIF from Texas Instruments. Here is the olimex schematic .
I built the programmer on a piece of breadboard and used the parallel port conversion. The MCP601 op amp is not produced in DIL package, but MCP602 is quite common. I also subtituted the stabilizer by Holtek HT71433A, which is much cheaper. I fixed the ribbon cable to the programming connector by a bit of hot glue.
After I built the programmer I found a weierd thing. In some parallel port configurations VDD was pulled considerably higher than 3.3V. The highest voltage mesured was 3.8V, which is on the boundary of maximal allowed voltages of the MPS430 microcontroller. The output of the OP AMP is pulled up by AI or SEL input signals (pins 14 and 17) of the parallel port. Because the power supply of the OP AMP is weak, the OP AMP is not able to regulate its output. I am not sure whether it is really a problem, but to be on the safe side I rewired the two pullup resistors R16 and R17 to the input of the stabilizer. Now the voltages at the programming pins are always lower than 3.3V. The programmer works reliably on my desktop PC.