Making a Programming Cable That Works With a CM300 Radio Making a Programming Cable That Works With a CM300 Radio By Robert W. Meister WA1MIK Problem: You acquired a CM300 mobile radio and want to program it. You notice there's a standard modular microphone jack on the front of the control head, so you fire up CPS, plug in your standard trusty modular programming cable, and the radio appears dead. No communications at all. Some quick research verifies that the same two pins (SCI and GND) are used for programming. You've used the cable to successfully program MaxTracs and other modular jack-equipped radios before, so why won't this one work? Well a bit more research might lead you to the CM300 Detailed Service Manual, which states: The HOOK line (J802-6) is used to inform the uP which type of microphone or SCI lead is connected to the microphone socket.

The voltage of the HOOK line is monitored by the uP (port PE0, MIC_SENSE) through a resistor divider on the main board. When the HOOK line is grounded (on hook condition) or floating (2.8V nominal), the uP sets the mux (U803) for keypad operation to allow the use of microphones with a keypad. When the HOOK line is connected to 9.3V, the uP sets the mux for SCI operation. This mode is also used to select low cost mic operation where the gain of the microphone path is increased (on the main board) to compensate for not having a pre-amp in the low cost mic. So it seems all you need to do is connect the HOOK line to a source of 9.3V, but where can you get that from? Solution: It turns out that the front panel MIC jack has assigned signals to the previously spare pins on older radio MIC jacks, including a convenient source of 9.3V, just what you need. Here are the signals on the various pins.

Mar 05, 2010 Motorola Tetra Radio, MotoTRBO Radio, Commercial Series Radio. Commercial Series Customer Programming Software. Flobo System Repair Lite 1.3. 100 personalities on CM340. Jan 02, 2013 This video shows you how to download the Motoroloa RDX Two Way Radio software to your computer. The video is brought to you by the Two Way Radio Center.

At some point Motorola changed the ordering of the pin numbers; in the past they started with pin 8 (RX Audio) at the bottom or left. When you look into the front of the CM300 radio with the notch (for the locking clip) on the bottom, RX Audio is still on the left but now they call that pin 1.

The signals are still physically on the same pins; only the pin numbering has been reversed. Pin Signal Name 1 RX Audio 2 SCI 3 Mic. Audio 5 GND 6 Hook 7 Boot_Res 8 9.3V The stock modular programming cable only uses pins 2 (SCI) and 5 (GND). Due to numbering differences, these correspond to pins 7 (SCI) and 4 (GND) on the MaxTrac, Radius, MaraTrac, GM300, CDM, and GTX radios. So all you have to do is add a jumper to your existing modular programming cable, inside the hood of the DB25 end, such that it connects the wires going to the modular plug pin 8 to pin 6. These wires should otherwise be unused. You should use an ohmmeter to verify the proper pins and connector orientation.

The original cable only made use of modular pins 2 and 5, and DB25 pins 1, 4, 11, and 15. The new and improved programming cable is now wired up thusly: Mod. Pin Signal Name DB25 Pin Notes 1 RX Audio None 2 SCI 15 Stock cable 3 Mic. PTT None 4 Mic. Gw Basic 64 Bit Version here.

Audio None 5 GND 1 Stock cable 6 Hook None Connect to pin 8 7 Boot_Res None 8 9.3V None Connect to pin 6 Note: Jumper: DB25 pin 4 must still be connected to DB25 pin 11. It seems simple, and it works great for the CM200, CM300, and PM400 radios, and probably a bunch of other commercial and professional radios made since the mid-1990s, and it will still work well with older radios. Cautions With Other Radios: MaxTrac, Radius, GM300, DeskTrac, SM50, SM120, M1225, R1225, CDM, and GTX radios either don't use pins 7 and 8 (what some of them refer to as pins 1 and 2), or supply only 5-8V or have a 27V Zener diode on the Hook line, so the added jumper will have no effect. However, you WILL have a problem if you use this modified cable on a MaraTrac.