[avrdude-dev] [bug #55884] ft232r communication fails on programmed part if miso line toggles

[Klaus Syttkus]

URL:
  <https://savannah.nongnu.org/bugs/?55884>

                 Summary: ft232r communication fails on programmed part if
miso line toggles
                 Project: AVR Downloader/UploaDEr
            Submitted by: mumpel
            Submitted on: Mon 11 Mar 2019 11:43:09 AM UTC
                Category: None
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: Klaus Syttkus
        Originator Email: 
             Open/Closed: Open
                 Release: 6.3
         Discussion Lock: Any
     Programmer hardware: ft232r
             Device type: t85

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Details:

I use the miso line for UART emulation on my ATtiny, so that I can use the
FT232R in ftdi_sio mode for communication.
In this configuration, reprogramming an ATtiny fails if the ATtiny produces
continuous traffic right after RESET ("Device is not responding to program
enable. Check connection").
This can be fixed by inserting a call to ft245r_drain in
ft245r_program_enable:

--- /tmp/avrdude-6.3/ft245r.c   2014-09-15 21:01:09.000000000 +0200
+++ ft245r.c    2019-03-11 11:21:14.798593714 +0100
@@ -387,6 +387,7 @@
     avr_set_bits(p->op[AVR_OP_PGM_ENABLE], cmd);
 
     for(i = 0; i < 4; i++) {
+        ft245r_drain(pgm, 0);
         ft245r_cmd(pgm, cmd, res);
 
         if (res[p->pollindex-1] == p->pollvalue) return 0;





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