[avrdude-dev] [bug #47890] ft232r serial dongle connected to ponyser interface

[Christian Mueller]

URL:
  <http://savannah.nongnu.org/bugs/?47890>

                 Summary: ft232r serial dongle connected to ponyser interface
                 Project: AVR Downloader/UploaDEr
            Submitted by: cm1
            Submitted on: Tue May 10 18:07:34 2016
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Christian Mueller
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any

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Details:

I tried to get a regular USB/RS232 adapter with an FT232R chip working on a
board/programmer using the "ponyser" interface using type "ftdi_syncbb".
However, the [oscillo]scope showed that both clk and mosi, which are inverted
in my configuration, jumped back to high levels directly after each command.

It turned out that ft245r_cmd(), line 518, finishes by simply sending a
0-byte, ignoring pins that might be inverted:


    for (i=0; i<4; i++) {
        buf_pos += set_data(pgm, buf+buf_pos, cmd[i]);
    }
    buf[buf_pos] = 0;
    buf_pos++;


The following should work better:


    for (i=0; i<4; i++) {
        buf_pos += set_data(pgm, buf+buf_pos, cmd[i]);
    }
    ft245r_out = SET_BITS_0(ft245r_out,pgm,PIN_AVR_SCK,0);
    ft245r_out = SET_BITS_0(ft245r_out,pgm,PIN_AVR_MOSI,0);
    buf[buf_pos] = ft245r_out;
    buf_pos++;


NOTE: The RS232 dongle still didn't work in the end but the scope showed
correct signal levels. It also showed, however, that my dongle apparently
doesn't provide enough current to switch the signals fast enough so that the
peak-to-peak voltage at the default baud rate for CLK was only around 2.5V...
I gave up on this for the time being - I still do have a regular RS232 port in
my computer - but I thought it would be good to keep track of the issue, hence
this bug report.

For what it's worth at this point, here's the configuration for this
combination (haven't checked whether MISO is inverted or not because I've
never seen anything on that pin):


# ponyser serial design with regular FT232R USB/serial adapter
programmer
  id    = "ponyser-ft232r";
  desc  = "ponyser serial design, using FT232R Synchronous BitBang";
  type  = "ftdi_syncbb";
  connection_type = usb;
  miso  = ~3;  # CTS
  sck   = ~2;  # RTS
  mosi  = ~4;  # DTR
  reset = ~0;  # TXD
;






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