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December 15, 2007
Product DEV-11575 |
about 3 months ago
There seems to be no shortage of threads about “Access denied” with genuine Arduino boards for that matter: https://www.google.com/search?q=access+denied"+site:arduino.cc
perhaps one of them holds the answer to your problem. For what its worth, I suspect any Access Denied error is due to a Windows software issue, and unlikely to stem from any difference between the genuine Arduino Uno and this board.
Product SEN-12566 |
about 6 months ago
Oh yes! Or just an arrangement of a SMT loading resistor + 2 pads for you to solder this on yourself. ADC6/7 just cry out for any use at all. Other ideas include pads for a SMT thermistor (again, would require a loading resistor) or the TMP36 temperature sensor. I’m not saying to increase cost by $1 by populating them, but give us some pads that might turn out to be useful.
Product DEV-11575 |
about 11 months ago
The BOM calls Y1 a 16MHz resonator, so I’m guessing it’s the less expensive and less accurate part. A typical* resonator has .5% tolerance, or 7.2 minutes/day, so it’s a poor solution for timekeeping needs.
*typical = first 16MHz SMT resonator I read a datasheet for
Yes, this board has the same functionality as the Arduino Uno: USBVCC is gated to +5V when VIN (barrel jack voltage) is below a threshold. Have a look at the “Comparator / 3.3V Regulator” section of the schematic as compared to the Arduino Uno reference schematic.
Product DEV-11575 |
about a year ago
Any tips on how to get eagle 5.6.0 free version to route this board? It seems to not want to route to those SMD headers, whether in autoroute or follow-me mode. I wanted to try modifying the board design with some of the ideas mentioned in this thread, but (re)routing everything is quite a chore.
5V according to the schematic. Color me confused that they don’t explicitly mention this in the bullet points.
Hey, just another crazy idea. The atmega328 in the surface-mount package has ADC6/7 pins, but these are no-connects in the redboard’s schematic. Why not route these to arduino pins A4/5 with surface mount jumpers (connected at the time of manufacture) to atmega pins ADC4/5.
As shipped this looks like it would be fully arduino-compatible (hm, possibly excepting input impedance of A4/5, so complicate the bridge a bit so folks affected by this can sever ADC6/7 from A4/5) but once the jumpers are cut you have 8 ADCs available, or you can use 2-wire serial and 6 ADCs simultaneously, all within the UNO R3 form factor.
Ascii schematic in case it clears things up (same for PC5/ADC7/A5/SCL):
PC4 ---+-(-|-)---- ADC6 (avr pin names)
SDA --' `------ A4 (arduino pin names)
with (-|-) representing a 3-way surface mount jumper (SJ2 or SJ2W) manufactured with all pads connected.
If you take a gander at the schematic, the Arduino’s pin 0/1 are connected to the FTDI chip as well as to the header. As a consequence, whatever the Arduino transmits will be received by the PC as well as by whatever is attached at pin 1. If something is connected at pin 0 it will override anything transmitted from the PC, as there is a resistor (1kΩ) between the FTDI chip’s TX output and the Arduino RX input.
I think this is true of most (all?) Arduino-compatible boards except the Leonardo, which is the one that uses a USB-capable Arduino (atmga328u4) as the main chip. This leaves pins 0/1 free when communicating with the PC.
How much power is it permitted for the LM1117 regulator to dissipate? Here’s my back of the envelope calculation:
With 15V in and 200mA 5V out (atmega328p absolute maximum DC current is 200mA), dissipation in the regulator is probably around 9V*200mA = 1800mW (assuming 1V dropped by diode D1, which is probably an overestimate). I don’t have much confidence in my ability to measure the heatsink area from the pictures, but the most optimistic values from Table 1 of the lm1117-n datasheet is 66°C/W for 1in² copper on the top side, or a rise of 119°C. At an ambient of 25°C this is just barely below the absolute maximum junction temperature of 150°C. You certainly can’t draw the same 500mA as you can from USB.
If we assume 1800mW is OK, then at the lower end of input voltage you could draw 900mA as you’re only dropping around 2V in the regulator.
I wonder how much sparkfun calculated it would cost to change from a linear regulator to a switching regulator; it would be great for a lot of uses if the board could supply 500mA under all conditions and (say) 1A when powered by an external 7-15V/1A DC power supply. A guy can dream, can’t he?
As a specific example, I have a sketch (well, it’s actually written in assembly and built with gcc at the commandline) that transmits flat-out at 200kB/s for weeks without hiccup. In one run I streamed about 900GB of data. As far as I’m aware, the USB-based Arduinos are not capable of this feat; they start losing serial data well before reaching this speed.
It’s no wonder: at this rate, a 16MHz AVR only gets 80 cycles per byte transmitted. It took careful planning and cycle counting to achieve the 200kB/s rate. (This uses a 2MHz serial rate, the highest rate common to a 16MHz AVR and the FTDI chip)
(The application is transforming biased bits from a hardware noise source into a high-entropy data stream; under a modest assumption about the noise source and the hash, the data stream can be shown to contain .9998 bits of entropy per bit of output. 200kB/s is a substantially higher rate than other similar designs I’ve found on the internet.)
No public wish lists :(