What is the maximum cable length?
Answer
(A) Maximum Cable Length
The maximum cable length depends on several parameters:
Cable structure: Unshielded, separate wires are recommended to reduce crosstalk and capacitance.
Microcontroller type: Some microcontrollers are highly sensitive to small voltage spikes on the clock, data, or reset/VPP lines.
Target PCB design: Components placed near the target microcontroller and the termination of the clock/data lines can significantly affect communication between the programmer unit and the target.
Other factors: Additional elements (such as layout or grounding) may also influence the ability to enter programming mode.
(B) Recommendation
We recommend using cables as short as possible. However, we are aware that several customers successfully use cables longer than 2 meters.
(C) Additional Filtering
To improve signal integrity with longer cables, you can add a small capacitor (approximately 22 pF) between the clock and GND on the target side of the cable.For reference, see the document: https://softlog.com/documents/Filter%20for%20long%20cables.pdf
