ispDownload cable

To program CPLD programmable logic) devices you only need very simple isp download cable. The cable is simple if we use computer’s printer port.

For my experiments I removed Lattice isp2032VE chip from old wireless router and soldered it to test PCB. This chip is supported by free licensed Lattice Semiconductors software. You can download software for free from Lattice web pages.

Somehow cable circuit diagram is hidden in Lattice pages, but while searching world wide web I found it. The first description was from Intel (!) web page. It is description of the cable and small schematics.
And from some personal pages I found full circuit diagram of Lattice ispDownload cable. It is universal isp and JTAG cable, but it is supported only by Lattice software.

New CPLD chips are 3.3V or less logic, but cable chips are powered by 5V. So don’t forget to use proper power supply voltage. My chip is 3.3V, but 5V tolerant, so no problems with interfacing with computer.

No need to build PCB for such small device, so I made everything in the “air” and glued with thermal glue.

ispDOWNLOAD Cable For Programming Lattice ISP Devices

These two resistors I added only to protect my computer if I’ll decide to connect the powered cable to computer. One resistor is connected to Vcc sense- I don’t like to put full Vcc power to my computer LPT port pin. Other resistor is connected between shield ground and data ground pins. When you connect the connector, the shield is connected first and all voltage difference with go threw this resistor first reducing possible power surges.

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