MicroFPGA
An affordable and open-source FPGA platform for the electronic control of microscope.
Register interface
The communication interface is based on the Register interface for the Mojo from Alchitry. The register interface allows reading/writing multiple times to the same address or to several consecutive addresses. MicroFPGA does not take advantage of this.
Each parameter in MicroFPGA has an address used for reading/writing its value that depends also on the channel of the signal it corresponds to (e.g. the id of the laser). MicroFPGA has the following parameters for the Au/Au+ (i.e. with analog read-out), with 1 camera (fixed), 8 lasers, 4 TTL, 7 servomotors, 5 PWM and 8 analog inputs (fixed):
| Signal | Parameter | Address | Range |
|---|---|---|---|
| Laser trigger | mode | Laser id (0-7) | 0-4 |
| Laser trigger | duration | 8 + Laser id (0-7) | 0-65535 |
| Laser trigger | sequence | 16 + Laser id (0-7) | 0-65535 |
| TTL | state | 24 + TTL id (0-3) | 0-1 |
| Servo | state | 28 + Servo id (0-6) | 0-65535 |
| PWM | state | 35 + PWM id (0-4) | 0-255 |
| Camera trigger | trigger mode | 40 | 0-1 |
| Camera trigger | start/stop | 41 | 0-1 |
| Camera trigger | pulse | 42 | 0-65535 |
| Camera trigger | period | 43 | 0-65535 |
| Camera trigger | exposure | 44 | 0-65535 |
| Camera trigger | delay | 45 | 0-65535 |
| Analog input (read only) |
value | 46 + Analog id (0-7) | 0-65535 |
| Version (read only) |
MicroFPGA version | 200 | 3 |
| ID (read only) |
Board id | 201 | 29, 79 or 80 |
The addresses are defined in the top file of the Alchitry Labs project. A read request is answered by 4 bytes representing the queried value. Note that unknown addresses will cause the FPGA to answer 11206655 (error code).
Read example
In order to read the current value of a parameter, we send 5 bytes. The first byte is a read request (where the most significant bit is 0), while the other 4 are the address. For instance, to read the 4th laser (laser id = 3) duration (address = 8+3), we send the following request to the FPGA:
| Byte 0 | Byte 1 | Byte 2 | Byte 3 | Byte 4 |
|---|---|---|---|---|
| read/write | address | address | address | address |
| 00000000 | 00001011 | 00000000 | 00000000 | 00000000 |
We then receive a 32 bits answer, with the least significant byte sent first. If the duration is 40 ms (value = 40’000, 1001110001000000 in binary), then the answer is the following:
| Byte 0 | Byte 1 | Byte 2 | Byte 3 |
|---|---|---|---|
| value | value | value | value |
| 01000000 | 10011100 | 00000000 | 00000000 |
Write example
Following the previous example, in order to change the 4th laser duration to 55 ms (value = 55000, 1101011011011000 in binary), we should write:
| Byte 0 | Byte 1 | Byte 2 | Byte 3 | Byte 4 | Byte 5 | Byte 6 | Byte 7 | Byte 8 |
|---|---|---|---|---|---|---|---|---|
| read/write | address | address | address | address | value | value | value | value |
| 10000000 | 00001011 | 00000000 | 00000000 | 00000000 | 11011000 | 11010110 | 00000000 | 00000000 |
Where we see that the write request is indicated by the most significant bit in the first byte, and that the value is sent with the least significant byte first.
Register interface implementations
Examples of the register interface implementations can be found here:
- C++: in the Micro-Manager device adapter, line 347 to 407.
- Python: in the MicroFPGA-Py library, line 42 to 81.
- Java: in the MicroFPGA-Java library, line 39 to 76.