Conv TTL Blocking issueshttps://ohwr.org/project/conv-ttl-blo/issues2019-02-12T09:59:21Zhttps://ohwr.org/project/conv-ttl-blo/issues/1Unnecessary pull-up resisors on flash chip2019-02-12T09:59:21ZDenia Bouhired-FerragUnnecessary pull-up resisors on flash chipAt the bottom of sheet 7, there are some pull-up resistors on the W\_n
and Hold\_n input pins of the flash memory. These (R195 and R230) are
unnecessary and those pins can be tied to Vcc P3V3
directly.
![](/uploads/07f9b214b534ef912052619ee57dca73/1507275917174-0.png)
Note that, if this (obsolete) flash chip is replaced, as per issue
\#1655, this work package can be ignored and closed.
### Files
* [1507275917174-0.png](/uploads/07f9b214b534ef912052619ee57dca73/1507275917174-0.png)https://ohwr.org/project/conv-ttl-blo/issues/2PCB layout: share pads between pul-up and pull-down resistors2019-02-12T09:59:22ZDenia Bouhired-FerragPCB layout: share pads between pul-up and pull-down resistorsIf a new version of the board is ever made, it would be a nice feature
to have the pull-up and pull-down resistors in the PCB version circuit
(sheet 4), share one pad. Since they can never be mounted at the same
time, this would resduce the risk for human error.https://ohwr.org/project/conv-ttl-blo/issues/3Pull-up resistors too strong2019-02-12T09:59:22ZDenia Bouhired-FerragPull-up resistors too strongSame as in issue \#16661, 10kOhm pull-up resistors should be used.https://ohwr.org/project/conv-ttl-blo/issues/4LED lines need pull-down resistors2019-02-12T09:59:22ZDenia Bouhired-FerragLED lines need pull-down resistorsLED lines from FPGA are negative logic and are connected to front and
rear panel LEDs through inverting schmidt triggers.
These LEDs are supposed to light up immediately at board power up, hence
why the negative logic is used. It was assumed that these lines will be
Low during FPGA configuration.
However, user I/O pins of the FPGA are set to be **floating** during
power up.
Moreover, the data sheet of the inverting schmidt triggers does not
recommend using floating inputs.
Although the correct behaviour is observed on prototypes, the use of
floating inputs on the schmidt triger may happen to be problematic in
noisy environments,
If a new version of this board is to be produced, pull-down resistors
are recommended at the input of the schmidt trigger inverters.https://ohwr.org/project/conv-ttl-blo/issues/17Ideas for similar designs2019-02-12T09:59:34ZErik van der BijIdeas for similar designsUnder this issue we can add features or ideas that came up after the
design was finished.
These ideas may be used for new designs.