Saturday, March 8, 2014

Z16F2810 Programmer

The last chip in the comparison of microcontrollers is the Z16F2810. It comes in PLCC and is the only part in the ZNEO line that isn't QFP only. In order to program the chip I soldered a PLCC socket to perfboard with headers for one of the GPIO ports and for an FTDI cable.

In the beginning I was excited about the PLCC socket but it turned out to be somewhat inconvenient to solder due to all the jumper wires needed to reach the inside row of pins. Next I connected the chip to the FTDI cable and tried to access it over UART as described in this Application Note about the bootloader. I had overlooked that the UART bootloader is not part of the ROM and has to be loaded over the one-wire interface normally used to program the chip. Until I realized this I removed the chip several times looking for faults in the circuit and managed to crack the socket with a screwdriver on the third removal. Zilog sells a specialized cable for programming their chips through the debug pin and I hoped to make something similar that would work over an FTDI cable. One forum post I found was really helpful. It showed what the cable looks like inside:

It seemed pretty unlikely that I could recreate this on my own. Later in the post someone mentioned that some of the Zilog documents show how to program the chip with a serial cable and only one diode. All I had to do was solder the diode and a 10k pull-up to the debug pin to make it work with the FTDI cable.

The next hurdle was the software. The picture above shows a USB SmartCable which will work with the ZNEO version of the ZDSII software Zilog offers for programming and debugging. The ZNEO version of ZDSII does not, however, work with the Serial SmartCable which the FTDI cable would replace. The Z8 Encore! version of ZDSII does support the cable. The same forum post explains that you can simply copy the file SerialSmartCable.xdt from the debugtools directory of the Z8 version to the debugtools directory of the ZNEO version. You will also need a copy of the file NxZNeoSerial.dll. Another website, also in German, explains that a copy of this file comes with Smart Flash Programmer 2.2.0.

The ZDSII IDE works well enough for writing code, although I still prefer to use Code::Blocks. The debugger is really handy. You can set break points and look at the disassembly compared to the C source as the program is running, as well as examine memory and registers. It is a little unwieldy, however, to go through the whole process of disconnecting, compiling, reconnecting, transferring, and restarting every time code is recompiled. In my opinion there should be a single button to recompile and run code. Another small gripe is that when code starts to run, the debugger automatically halts on the first instruction and jumps to that place in the source. Unfortunately, that is always start-up code, so every time you press Go it opens the start-up assembly file supplied with the compiler and waits for you to continue. This is just annoying since it has to be closed every time.

The IDE uses make with its own compiler. Running this compiler from the command line shows that there are many compiler options but the only one available in the IDE is "Limit Optimizations for Easier Debugging." There is no way from the IDE to specify arguments to optimize for speed or size specifically. You can, however, export a makefile from the IDE and run make on its own. Doing this I was able to edit the makefile to add the flags for speed and size optimizations but neither of them produced any difference. I copy the file generated by make to the output directory of an empty project that I keep open in the IDE. Because compiling is done outside of the IDE, I can upload the file to the chip without having to disconnect and reconnect.

1 comment:

  1. Hi, can you please add: 'Zilog', 'Zneo' labels to your post that would make it easier to be found by search engine like google, etc. Because people may not have the same part number MCU as you and because of that use general terms.

    Thank you.