I'm a new HAM member in this awesome community, so please take everything with a grain of salt. First of all, I DO NOT want any CPS programs! Just wanted to make that clear.

Recently, I've received a donation of 4 old salvaged Entel HTs, which I'm trying to use mostly for experiments and learning the basics of the internals. Among those I managed to bring it to life of an HT880 UHF handheld, which is working surprisingly good with the already programmed channels. Then I contacted the manufacturer's official support channels for help with the programming, they have provided the CPS but due to the very old model, programming guide & cable for this specific radio is long discontinued and even if someone has one to sell it to me, shipping radio related products to Bangladesh is very difficult. What can I do? I just can't seem to abandon this good working radio, amateur practice is very difficult but changing rapidly here in Bangladesh.

Now, I'm familiar with programming common brand radios and serial communication basics, I was wondering if it's possible to figure out the pinout and build a programming cable with a USB to Serial Board.

  • $\begingroup$ What is CPS? I'm not familiar with that. $\endgroup$ Commented Feb 3 at 20:22
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    $\begingroup$ @Mike Waters I think CPS originated with Motorola -- "Customer Programming Software" $\endgroup$ Commented Feb 5 at 6:23
  • $\begingroup$ Ah! This is far more a recent product that I have expected it to be when you said "old" and "very old model": This was still being sold at least between 2006 to 2008 by ENTEL, so, it's not really that old. That makes it a bit more guesswork what the device speaks – it's entirely feasible that it contains a USB interface itself, but it's more likely it's something UART/TTL . I'd recommend trying to figure out which by looking for USB-typical termination resistors on the board between programming connector and first digital-looking chip connected to that. $\endgroup$ Commented Feb 5 at 11:58
  • $\begingroup$ @user3486184 reading their website, ENTEL seems to restrict programming of these devices to licensed dealerships (as in: can't even buy the programming manual without being a licensed dealer), but yeah, the name seems to have stuck for some reason. $\endgroup$ Commented Feb 5 at 11:59
  • $\begingroup$ @MarcusMüller I'll try that and let you know, thanks $\endgroup$ Commented Feb 5 at 21:05

1 Answer 1


Without access to documentation, this is an exercise in reverse engineering.

You'd first want to figure out the physical properties of the programming link. Is it a serial or a parallel bus? Something you might probably infer from the number of pins. If in doubt, assume serial.

Electrically, that connection might simply be compatible with TTL, but they might also be differential, or totally different voltage levels, or actually a current-based scheme, and whatnot. Here, you'd however stand the best chance of finding documentation of other devices from the same series.

Then, you'd need to figure out what the signaling looks like. Is it something complex like UART (which is what your USB-to-serial device does, typically at TTL voltage levels), or something simple like SPI, where the programming has an explicit clock line to signify when the bits are to be read? Your best bet as forming a working hypothesis on that is to look how complicated the programming cable looks like, from when it is and how it connects to a PC. If it's old and looks simple, then it's (at most) only changing voltage levels, most likely, and whatever connection to the computer it uses is logically what it uses with the handset.

Figuring out the pin out on the HT is mostly an exercise in looking at which components connect to the programming connector on the board. For example, it would be pretty simple if you found an rs232 voltage converter chip in your HT that connects to the programming connector. That has definite Rx and tx pairs, and all you need to connect to it would be a PC with an RS-232 port configured to the same settings (baudrate, start and stop bits, parity, use of RTS/CTS), or a USB-to-serial converter with rs232 voltage levels, and the ability to work with the same settings (not every usb-to-serial converter even has rs232 support).

Once you're somewhat confident you found the right pins and a nice of communicating that won't physically damage HT or computer or adapter, you'd need to figure out the logical protocol. This would usually be covered in programming manuals, so maybe you find an old scan of one? If not, the usual way for industrial controls, and I'd guess also for programming old handsets, is getting a hold of the software, and running it in an emulator, looking what it tries to send to external devices, sending that, seeing what you get in response, using the emulated external interface to tell the software that it's what you got from the device, and repeat that until you understand what needs to be done.

Sometimes, such software is pretty resistant to such attempts - the emulator might not emulate the necessary platform exactly enough, things are too timing-sensitive, or the software just buggy. In that case, you'd disassemble the CPS and do a purely analytical reconstruction of how the software interacts with the HT.

Armed with that knowledge and a cheap logic analyzer, you'd prototype your own signal conversion if necessary and your own programming software, and iteratively improve it till you succeed in programming your HT :)

  • $\begingroup$ 1. Couldn't find the appropriate programming cable to the same series, but a close similar series HTs uses a Prolific CP2303 USB-to-UART/RS232 chip based cable. 2. The programming interface is a standard 2.5mm audio jack with 4 possible pins. 3. I tried to read using an FTDI FT232RL USB-to-UART adapter with no luck using various pin configuration. $\endgroup$ Commented Feb 5 at 22:39
  • $\begingroup$ 3. I've noticed that the later series of HTs requires the radio to be in programming mode by pressing a combination of keys during powerup, and the LCD shows "Programming Progress", but I don't think HT880 requires that step because it has limited lcd, regardless tried various common button combinations, didn't work. $\endgroup$ Commented Feb 5 at 22:39
  • $\begingroup$ Yeah you're not going to get there without measurement equipment and access to the board. Also, an inspection of the components on the board will be central. If you can get access to the main microcontroller, you might be able to dump its firmware, unless it's properly locked down. From there, you could try reverse engineering a protocol. You won't solve this by just trying to plug in a serial connector and hoping it does something! $\endgroup$
    – sina bala
    Commented Feb 6 at 2:42

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