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1  Using Arduino / General Electronics / Re: SN74LS06 CMOS? on: June 12, 2014, 06:28:13 pm
Thanks!

I'm switching to a smaller IC.  With that IC, I should be able to use 0603 resistors.  0603 is small enough.
2  Using Arduino / General Electronics / Re: SN74LS06 CMOS? on: June 12, 2014, 03:23:02 pm
Why not use a voltage divider and connect directly to the uC.

If you read the datasheet for 74LSXX you need pullups on all not used inputs for the whole temperature range.
TI MUST print that.
In real life, it works for 99.9 % of all cases but in some cases the leakages are to big and the input goes low.

SMD?

Pelle

Yes, it is a SMD design.  I completed the layout then I realized that the inputs may float.  The customer requirement is not clear about this detail so I'm assuming the worst.  I only have the space of a 20-SOIC package left.  I don't think I have enough space for five voltage dividers.  Where is the leakage keeping from if the inputs are left open.
3  Using Arduino / General Electronics / SN74LS06 CMOS? on: June 12, 2014, 02:38:38 pm
I think I found an error in a TI datasheet, and I want to ask whether others see it as an error as well.  I need five digital inputs to my circuit.  The voltage levels it will see are 0V, 5V and open.  I don't want to use pull-up or pull-down resistors because simply I don't have the space.  I don't even have 0.1" for a SIP package.  So, I want to use the following open-collector inverter and I will use pull-ups in the microcontroller.  The microcontroller is uses 3.3V.  I thought the SN74LS06 was a BJT based device, but Note 4 on page 3 of the datasheet says that all unused inputs need a pull-up or pull-down resistor.  The schematic on page 2 shows BJTs (actually Schottky transistors).  What should I believe?

http://www.ti.com/lit/ds/symlink/sn74ls06.pdf
4  Using Arduino / Programming Questions / Re: upload firmware over half duplex RS-485 on: February 28, 2014, 09:19:49 pm
It worked for me.
5  Using Arduino / Programming Questions / Re: upload firmware over half duplex RS-485 on: September 12, 2013, 02:23:38 pm
Thank you for answering my question.  For the reset, I will just jerry-rig something up to cycle the power.  That won't be a problem.  BTW, I'll have to modify the bootloader to control the TX enable pin of the RS-485 transceiver which shouldn't be a problem either.  Thank you!
6  Using Arduino / Programming Questions / upload firmware over half duplex RS-485 on: September 12, 2013, 11:52:30 am
Does the Arduino bootloader work in a half duplex manner?  I have used the Arduino bootloader for my own personal projects with great success.  I have a new project that has a "two-wire" (half-duplex) RS-485 serial interface.  Once the board is in its housing, the ISP connector is difficult to access.  I was wondering could I use the RS-485 interface to program the chip.  I'm using the hardware UART of the chip for the RS-485 interface.  The essence of my question is can the bootloader work in a half duplex manner.
7  Using Arduino / Programming Questions / Re: Problem with ModbusMaster library on: June 06, 2013, 10:37:53 am
Post as much of the code as you can.
8  Using Arduino / Programming Questions / Re: T0/T1 internal pull-ups on: May 02, 2013, 03:29:33 pm
It works!

Code:
void setup() {
  Serial.begin(9600);
  pinMode(5, INPUT_PULLUP);
  TCCR1A = 0;
  TIMSK1 = 0;
  TIFR1  = 0;
  TCCR1B = _BV(CS12)
         | _BV(CS11);
  TCNT1 = 0;
}

void loop() {
  Serial.println(TCNT1);
  delay(1000);
}
9  Using Arduino / Programming Questions / Re: T0/T1 internal pull-ups on: May 02, 2013, 02:58:49 pm
Pull-ups are for *inputs*.  Clock sources are *outputs*.

I think there is some confusion...  T0 and T1 are inputs (see section 14.3.3 of the datasheet).  I probably should have said that I want to select them as the clock source. 

And a base resistor connects between a pin and the base of a transistor.  A pullup connects between the pin and Vcc.  How that can replace a base resistor I'm not quite sure...

I want T0 or T1 to be held high while the transistor is off and pulled low when the transistor is on.  The transistor in this case is a photo-interrupter.
10  Using Arduino / Programming Questions / Re: T0/T1 internal pull-ups on: May 02, 2013, 02:38:15 pm
Why? When the pins are outputs/clock sources, the 40mA drive capability will far outweigh the 0.25mA an pullup can offer.

I want to connect it to the collector of a transistor without having an external resistor.
11  Using Arduino / Programming Questions / T0/T1 internal pull-ups on: May 02, 2013, 02:04:57 pm
Is it possible to use the internal pull-ups on pins T0 and T1 while using them as clock sources?  If it matters, I'm using the ATmega328P chip.
12  Using Arduino / Networking, Protocols, and Devices / Re: DHCP testing tool on: January 29, 2013, 02:01:06 pm
http://www.vercot.com/~serva/
13  Using Arduino / Networking, Protocols, and Devices / Re: DHCP testing tool on: January 29, 2013, 11:24:29 am
Good questions... I will try different DHCP server implementations, but I was interested in see how it would handle non-typical DHCP information.  It has been years since I have read about what can be put in DHCP packets.

The program named Serva looks interesting.
14  Using Arduino / Networking, Protocols, and Devices / Re: DHCP testing tool on: January 28, 2013, 03:41:01 pm
I realize I wasn't clear about what I was asking.  I want to try different DHCP server settings to see if my device handles them correctly.  DHCP can do a lot more than just hand out IP addresses.  I'm afraid that my device will work fine with my DHCP server, and when it becomes time to ship it to the customer, it won't work on their server.

I know and use Wireshark.  I've been using it since it was named Ethereal. 
15  Using Arduino / Networking, Protocols, and Devices / DHCP testing tool on: January 28, 2013, 02:41:01 pm
Is there a recommended software program to use to test/exercise the networking stack particularly DHCP?  I'm going to develop an Ethernet based product, and currently, I'm creating a plan for the project which includes how it will be tested.
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