The SQ50 consists of the following components:
BOM
- Top side:
- Board markings: "SQ200", "SQ Series V1.4"
- LED: status (green: application mode: orange: bootloader mode OR capture mode)
- MicroUSB-connector (to the host computer)
- 5-pin 2.54mm pin header, for probe IO
- Xilinx Spartan XC3S50AN TQG144AGQ1917 D5886160A 4C (QFP-144) (datasheet with pinout, internal flash memory docs)
- ISSI IS61WV25616EDBLL-10TLI EAB217P5 1950 (TSOP-44, datasheet) (SRAM used for storing samples)
- FTDI HWJFS.00 FT240XQ 1741-D (USB interface) (product info, datasheet, proprietary drivers used by ScanaStudio)
- TI OPA 4354A 912Q (quad opamp, product info)
- A number of analog components
- Bottom side:
- 8-pin 1.25mm JST connector (JTAG)
- 3 empty slots/solder pads for more ISSI SRAM chips (probably used in the SQ100/SQ200 variants)
- Empty solder pads for a SOIC-8 chip for unknown purpose
- 147776 TP949 6EAL (QFN-16, unknown purpose)
- A crystal oscillator, frequency/markings are impossibly tiny to read
Photos
Outer shell:
Top side of the PCB:
Bottom side of the PCB:
JTAG connector
NOTE: THIS CONNECTOR USES 2.1V LOGIC LEVELS
The board has an 8-pin 1.25mm-pitch JTAG connector (JST-ish, compatible with Molex PicoBlade or Multicomp Pro 34443/34453) on the bottom side, under the USB connector. (Connection hasn't been tested with a JTAG probe yet, though. The pins have been checked with a continuity tester that it goes to the Spartan-3AN JTAG pins.) The pinout is as follows:
_________
|top side |
\ w/ usb/
|_____|
======================
_________________
| 1 2 3 4 5 6 7 8 |
| ' ' ' ' ' ' ' ' |
bottom side, jtag conn
- unknown/not connected
- unknown/not connected
- TMS
- TDO
- TDI
- TCK
- GND
- VCC
Perhaps the two 'nc' pins go to a different chip.
this repo has an adapter PCB design for 2.54mm JTAG or an ARM Cortex (Samtec FTSH) connector to this one. Parts tested to work are the Multicomp Pro MC34453 (connector) and Molex PicoBlade 15134-080x (cable).
Upgrading your device
When using a custom driver (and not ScanaStudio), my SQ50 seems to happily sample at 200 MHz when specified in the settings, even though it is not marketed to be able to do this.
However, unlike the SQ200, it has much less SRAM for storing samples. This can probably be fixed by populating the 3 empty pads intended for ISSI chips. This has not been tested yet, though.
You can get these ISSI SRAM chips here:
NOTE / WARNING
I tried installing 3 extra RAM chips, and, despite the contacts looking fine, the following happened:
- The device LED did not turn on
- USB enumerated properly, ScanaStudio recognised the device
- Starting an acquisition does not work, as the Spartan-3 gateware seems to refuse to do anything
This could either be bad power contacts, or something inside the Spartan-3 gateware stopping it from functioning. I suspect it is the latter, because (in my opinion) the contacts of the newly soldered RAM chips looked fine, soldering them off one by one did not fix the issue, and the most suspicious-looking contacts were not power-related.