This year in lab_2 we will solder a USB-microcontroller board named bronze_v2. Bronze has includes Red/Green/Blue LED and LDR (=Light Dependent Resistor), and uses a USB host plug so you can plug it directly into a computer, or use a USB extension cable to put it somewhere else.
To assemble your bronze PCB you will arrange an appointment at the Institute of Neuroinformatics (http://www.ini.uzh.ch), which is located at UZH (Irchel or Milchbuck tram stop), building 55, floor G, electronics workshop, directions here.
Please follow the detailed steps below. Videos will help you see exactly how to do various steps.
Parts are kept in the ring folder in transparent envelopes. Each envelope is labeled with the bronze board part designator, e.g. R5, D1, etc.
Please put the parts back immediately after taking them out. And make sure that parts go back inside the labeled bag for each part!!!!!!!
Your setup for assembling SMD prototypes consists of
' and'rosin-core solder wire. Both are useful.
Before starting with this step, watch this video: http://youtu.be/4_XqoapZ5Qk to see in general how to solder small 2 pin parts.
In this video you the assembly and testing of some components on the bronze board which are simple to solder is shown.
On the bronze board, start with soldering the following
Your soldering should end up shiny and bright and should clearly flow up from the pad onto the pin of the part. The image below shows a resistor that was not soldered correctly. Do you see how the solder has not flowed up onto one pin of the resistor?
When you solder the USB connector:
A properly soldered USB header is next:
After all these components are soldered, the blue LED should go on once you connect your board to a computer. You should start however, by connecting the board to the current-limited power supply (limited to about 100mA) with the USB micro plug on it. That way, if you have a short, you will not trip the overload protection on the laptop USB hub.
The orientation of the LED is shown here; the dot on the LED points away from the USB connector and the right side is the cathode (negative) side of the LED:
When you solder the USB connector, make sure not to short the metal case to any of the pins. It should end up looking like this:
The power LED should light up when you plug it into the USB cable connected to the current-limited power supply and the board should consume less than 20mA.
If you don't have this current-limited supply, then the power LED should light up when you plug in the board to a computer, and you should check that the voltage across C2 is within 5V +/- 5%.
Next we'll solder the voltage regulator that makes 3.3V from the USB 5V VBUS and some power supply bypass capacitors.
Measure the 3.3V rail voltage over C3 or C4. The voltage must be within 3.3V +/- 5%. And again, the current-limited supply should not consume more than about 20mA.
Before soldering the next components, watch this video: http://youtu.be/uPbjyeJypcg
When soldering the AVR32, in case you create bridges between the microcontroller pins: * make sure that they don't have to be there: Check with a blank PCB whether the two pins are connected by a trace directly in between. On the bronze board, no pins are shorted by direct traces between the pins. * Remove extra solder to clear the bridge:
Here's what it looks like:
Now it is time to solder:
When handling U1, be careful not to bend any of the pins. If you drop U1 on a hard surface the pins will almost always be bent on the corner and it is very difficult to straighten them. Be careful bending the pins in any case; they are brittle and will break off easily.
When you place the AVR32 on the board, make sure the pin 1 dot points as shown towards the USB connector. You can also see a pin 1 dot on the PCB. Someone once soldered the part at 90 degree angle. It is possible to remove the AVR32 but requires multiple soldering irons and also the use of 'ChipQuik', or else a hot air pencil. And it is not so easy. So make sure the orientation is correct…
When you solder U1, make absolutely certain that the part is lined up properly on all four sides after you solder only one corner pin. If the alignment is not correct, fix it before soldering any other pins. Once you solder one corner correctly, solder the opposite corner. If everything is lined up properly, then solder one of the sides that has no solder. Now the rest should be easy. Do not mash the pins, a gentle touch of the soldering iron is all that is needed. If you bend the pin while soldering it is very hard to get it back on top of the pad. To solder the pins, apply a bit of thin wire solder to the iron tip and get it to flow onto the pins and pads. A bit of liquid flux applied to the line of pads helps in this case quite a bit. Usually only a single bit of solder, or maybe two, is enough for all the pins on one side.
If you are confident that U1 and X1 have been soldered correctly, you can solder the remaining (easy) components. Refer to the schematic for values. All parts are in the folder of parts labeled by part number.
There is one component on the back side of the board, L2, which should just be a shorting jumper. Solder a 'zero ohm resistor' (a jumper). This connection isolates the AVR analog supply voltage. If you forget it nothing will work!
Your board should now look like this (except you will not have the LDR or RGB LED):
When you solder the button switches, make sure not to short any of the pins or the case:
Look at your board under the high power microscope. Look especially between the pins. You should not have leftover solder balls! If there are too many they will cause a short - maybe not today but later on. In any case, your solder joints should be shiny and clean and clearly weld the pins to the pads with nice wedges.
First, plug your board into the current-limited supply with the USB cable on it. If your board draws too much current the voltage will drop. A working board draws <40mA @5V. If your board draws too much power you must find the short(s) and fix it/them.
Next, after plugging in the board to a computer, check all rail voltages again:
|Measurement Site||Nominal Value|
|C1 or C2||5.0V +/- 5%|
|C3 or C4||3.3V +/- 5%|
|C7 or C8||1.8V +/- 5%|
If any of the voltages are out of range disconnect the board immediately and start visual inspection, and have someone else look at the board.
If you have an oscilloscope, let's check the oscillator: * Attach a wire to some GND pin. * Connect the scope ground clamp to the wire * Check the signal on C5 or C6, on the signal side, not the ground side. * You should see a (more or less sinusoidal) 12MHz signal with about 1Vpp amplitude.
Connect your board to a Windows computer and in the Device Manager you should see the AVR32 USB DFU device show up (if you installed the driver earlier).
Or, connect your board to a Linux computer, then run the command lsusb in a shell.
Besides other devices you should see:
Bus ??? Device ???: ID 03eb:2ff6 Atmel Corp.
To get further information on what Linux found out about the device, run sudo lsusb -d 03eb:2ff6 -v
You should get this: <code>
Bus ??? Device ???: ID 03eb:2ff6 Atmel Corp. Device Descriptor:
bLength 18 bDescriptorType 1 bcdUSB 2.00 bDeviceClass 0 (Defined at Interface level) bDeviceSubClass 0 bDeviceProtocol 0 bMaxPacketSize0 64 idVendor 0x03eb Atmel Corp. idProduct 0x2ff6 bcdDevice 10.00 iManufacturer 1 ATMEL iProduct 2 AT32UC3B DFU iSerial 3 1.0.2 bNumConfigurations 1 Configuration Descriptor: bLength 9 bDescriptorType 2 wTotalLength 27 bNumInterfaces 1 bConfigurationValue 1 iConfiguration 0 bmAttributes 0xc0 Self Powered MaxPower 100mA Interface Descriptor: bLength 9 bDescriptorType 4 bInterfaceNumber 0 bAlternateSetting 0 bNumEndpoints 0 bInterfaceClass 254 Application Specific Interface bInterfaceSubClass 1 Device Firmware Update bInterfaceProtocol 2 iInterface 0 Device Firmware Upgrade Interface Descriptor: bLength 9 bDescriptorType 33 bmAttributes 15 Will Detach Manifestation Tolerant Upload Supported Download Supported wDetachTimeout 0 milliseconds wTransferSize 65535 bytes bcdDFUVersion 1.01
Device Status: 0x0001
Now solder the 2×16 pin round pin gold plated headers into the bottom of the board to allow you to plug the bronze board into a solderless breadboard, as shown below. (Someone actually soldered the pins to the wrong side once.) Solder the thin pins from the bottom into the board so that the thick tough part sticks out. You will need to cut apart some pieces. Make sure the pins are nicely vertical and properly aligned so that you can plug the bronze board into the solderless breadboard later. Do this by solderining just one pin at the end of the strip and while the solder is hot you can make the pins at 90 degrees right angle. Then you can solder the rest of the pins.
Finally, you can solder the LDR and RGB LED if you want to run this test.
The LDR is not polarized.
The RGB LED has one ground cathode pin and 3 positive anode pins, one for each color. It is oriented as shown below, with the flat side of the LED to right right when you look at the board from the end; the long wire of the RGB LED is third from the left:
You made it till down here? Congratulations! Your board passed all tests that do not require a test-firmware to be flashed…
Your board will end up looking like this:
Use the flux remover spray and brush to clean off flux and solder balls. You can blow the board dry with the pressurized air. Don't use too much flux remover because it is expensive.
See the following documentation for more information. Remember we are using the AT32UC3B1256 and assembling the bronze_v2 board.
Further info on the original copper board: http://store.stackfoundry.com/dev-tools/copper-avr32-stick.html