Ideally each differential pair would have the same trace length and impedance etc, but it is slightly less important over the 4 pairs and more important between the two wires of any pair. My own motherboard uses an HDMI connector on P2 pins P40-P47 which are close to the middle of Peter's board and of shorter length. How about HDMI output? Are particular pins recommended for this and do they need special treatment, such as equal trace lengths and other design when I can hopefully get my hands on one of these P2D2's I want to try HDMI output from this P2D2, at least experimentally.
#Inexpensive usb p2 card reader serial
But the monitor chip also measures the temperature and can also report actual A/D levels etc.īTW, the DTR signal was originally meant to monitor the DTR of a cheap USB serial converter and generate the reset pulse but since I upgraded the monitor to a USB version, there shouldn't be any need for that now. As for the XIN on the monitor that may not get connected since it would have to run across the board but the idea was so that the monitor could possibly drive the XIN of the P2 if necessary since the Silabs chip has a 1.5% 48MHz precision oscillator that could replace other clocking options (as an option).
#Inexpensive usb p2 card reader manual
But the RESn is also an input to the monitor so that it can detect both the very short pulses from a PropPlug or the manual reset button which can be used to force a particular boot mode. If I write some routines for the P2 then it can also setup the clock gen too.Īs for the DTR signal I shouldn't need it directly as the USB serial firmware will be enhanced to automatically generate a nice reset pulse and also make sure that the P2 doesn't boot from Flash/SD when loading from serial. The clock gen has OTP that can be programmed to load into its registers at reset so that I can set this up when it is assembled and tested to output a clock automatically. So the monitor can communicate with the P2 and vice-versa via I2C so that the monitor could load the clock gen although I don't think that will be necessary. I am hoping that SCL/SDA will be on P58,59 and I see no reason why not since I2C not only needs a valid start condition and address but it also filters any glitches which is what these signals would look like when operated in SPI mode. PCB layout will be posted in the next day or so and I will get this artwork sent off this week which means that I can have pcbs next week and I still have about a dozen P2-ES chips I can use. Because this regulator is adjustable I can boost up the 1.8V supply if needed but the main purpose is so that I can pre-regulate into a dual 3.3V LDO to deliver a clean output at fairly high efficiency still. The power section can use an MPM38111 for 1Ax2 outputs or an MPM38222 if we actually really needed 2A although I am using the 2A version on the prototypes.
What is the best arrangement for HyperRAM? My HyperRAM board will be a thin pcb that sandwiches onto the back of the P2D2 so it will probably only span a small section of the P2D2. I will probably use resistors to connect these to the closest I/O which at present is P32, P33. I like the Si3531A clock option because the chip is cheap and so are the crystals but I'm not sure where best to run the other two clock outputs.
The Silabs micro will probably do some smart resetting so that amongst other things any DTR style reset will always cause it to boot serially and ignore the Flash and SD. There's still some fiddling to do with the circuit including the oscillator options. It is still being updated but it should give you an idea of what to expect. Here is the latest schematic for the new P2D2.