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LimeSDR-Mini v1.2 hardware description

1 LimeSDR-Mini Board Key Features

The LimeSDR-Mini is low-cost software defined radio board. LimeSDR-Mini development board provides a hardware platform for developing and prototyping high-performance and logic-intensive digital and RF designs using Intel’s MAX 10 FPGA and Lime Microsystems transceiver.

Figure 1. LimeSDR-Mini v1.2

LimeSDR-Mini board features:

  • USB 3.0 controller: FTDI FT601
  • FPGA: Intel MAX 10 (10M16SAU169C8G 169-UBGA)
    • 169-pin FBGA package
    • 16 K LE
    • 549 Kb M9K Memory
    • 2368 Kb User Flash Memory
    • 1x fractional phase locked loops (PLLs)
    • 45x 18x18-bit multipliers
    • 130x general purpose input/output (GPIO)
    • Single supply
    • Flash feature
    • FPGA configuration via JTAG
  • RF transceiver: Lime Microsystems LMS7002M
  • EEPROM Memory: 2x 128Kb EEPROMs for LMS MCU firmware and FPGA data
  • FLASH Memory: 4Mb Flash memory for FPGA data
  • Temperature sensor (unpopulated)
  • General user inputs/outputs:
    • 1x Dual colour (RG) LED
    • 8x + 2x FPGA GPIO pinheader (3.3V)
  • Connections:
    • USB3.0 (type A) plug
    • Coaxial RF (SMA female) connectors
    • FPGA GPIO headers (unpopulated)
    • FPGA JTAG connector (unpopulated)
    • FAN (5V or 3.3V) connector
  • Clock system:
    • 40.00MHz onboard VCTCXO
    • Possibility to tune VCTCXO by onboard DAC
    • Reference clock input and output connectors (U.FL)
  • Board size: 69mm x 31.4mm

For more information on the following topics, refer to the respective documents:

  • FTDI FT601 USB 3.0 to FIFO Bridge datasheet [link]
  • MAX 10 FPGA device family, refer to MAX 10 Device Handbook [link]
  • LMS7002M transceiver resources [link]

2 Board Overview

This section contains component location description on the board. LimeSDR-Mini board picture with highlighted connectors and main components is presented in Figure 2 and Figure 3.

Figure 2. LimeSDR-Mini v1.2 board top connectors and main components

Figure 3. LimeSDR-Mini v1.2 board bottom connectors and main components

Board components description listed in the Table 1.

Table 1. Board components
Featured Devices
Board reference Type Description
IC1 FPRF Field programmable RF transceiver, LMS7002M
IC5 FPGA Intel MAX 10 (10M16SAU169C8G 169-UBGA)
IC6 USB 3.0 microcontroller FTDI USB 3.0 to FIFO interface bridge chip FT601
Miscellaneous devices onboard
IC8 IC Temperature sensor, LM75
Configuration, Status and Setup Components
J3 JTAG chain connector FPGA programming pin header on the board edge for Altera USB-Blaster download cable, 0.1” pitch
J4 JTAG chain connector FPGA programming pin header for Altera USB-Blaster download cable, 0.05” pitch
LED1 or LED2 LED1 or LED2c USB3.0 microcontroller (IC13) boot configuration (PMODE0[2:0]) resistors. Default mode: SPI boot, On Failure - USB Boot
General User Input/Output
J5 Pin header 8x FPGA GPIOs, 3.3V, 0.05” pitch
J6 Pin header 2x FPGA GPIOs on the board edge, 3.3V, 0.1” pitch
J10 Pin header 5V (3.3V voltage can be chosen by resistors) fan connection pin headers, 0.1” pitch
Memory Devices
IC2 IC I²C EEPROM Memory 128Kb (16K x 8), connected to RF transceiver I2C bus
IC10 IC I²C EEPROM Memory 128Kb (16K x 8), connected to FPGA I2C bus
IC11 or IC11A IC11 Quad SPI Flash Memory 4Mb (512K x 8), connected to FPGA SPI
Communication Ports
J7 USB3.0 connector USB3.0 connector
Clock Circuitry
XO1 VCTCXO 40.00 MHz Voltage Controlled Temperature Compensated Crystal Oscillatorc
IC9 IC DAC for TCXO (XT4) frequency tuning
IC7 IC7 Clock buffer
J8 U.FL connector Reference clock input
J9 U.FL connector Reference clock output
Reference clock output
IC12 IC Switching regulator (1.8V)
IC13 IC Switching regulator (3.3V)
IC14 IC Linear regulator (2.5V)
IC15 IC Linear regulator (12.5V)
IC16 IC Linear regulator (1.4V)

3 RF Frequency Range

LimeSDR-Mini board covers RF frequency range from 10MHz up to 3.5GHz. There are different matching networks connected to the RF transceiver RF inputs and outputs (antennas):

  • Use TX1_1 RF output for 2GHz - 3.5GHz frequency range
  • Use TX1_2 RF output for 10MHz - 2GHz frequency range
  • Use RX1_H RF input for 2GHz - 3.5GHz frequency range
  • Use RX1_W RF input for 10MHz - 2GHz frequency range

4 LimeSDR-Mini Board Architecture

The heart of the LimeSDR-Mini board is Intel MAX 10 (10M16SAU169C8G 169-UBGA) FPGA. It’s main function is to transfer digital data between the PC through a USB3.0 connector. The block diagram for LimeSDR-Mini board is presented in the Figure 4.

Figure 4. LimeSDR-Mini Development Board Block Diagram

4.1 LMS7002M Based Connectivity

The interface and control signals are described below:

  • Digital Interface Signals: LMS7002 is using data bus LMS_DIQ1_D[11:0] and LMS_DIQ2_D[11:0], LMS_ENABLE_IQSEL1 and LMS_ENABLE_IQSEL2, LMS_FCLK1 and LMS_FCLK2, LMS_MCLK1 and LMS_MCLK2 signals to transfer data to/from FPGA. Indexes 1 and 2 indicate transceiver digital data PORT-1 or PORT-2. Any of these ports can be used to transmit or receive data. By default PORT-1 is selected as transmit port and PORT-2 is selected as receiver port. The FCLK# is input clock and MCLK# is output clock for LMS7002M transceiver. TXNRX signals sets ports directions. For LMS7002M interface timing details refer to LMS7002M transceiver datasheet page 12-13. [link].
  • LMS Control Signals: these signals are used for optional functionality:
    • LMS_RXEN, LMS_TXEN – receiver and transmitter enable/disable signals connected to FPGA Bank 8 (VDIO_LMS_FPGA; 2.5V).
    • LMS_RESET – LMS7002M reset connected to FPGA Bank 7 (VDIO_LMS_FPGA; 2.5V).
  • SPI Interface: LMS7002M transceiver is configured via 4-wire SPI interface; FPGA_SPI_SCLK, FPGA_SPI_MOSI, FPGA_SPI_MISO, FPGA_SPI_LMS_SS. The SPI interface controlled from FPGA Bank 2 (VDIO_LMS_FPGA; 2.5V).
  • LMS I2C Interface: can be used for LMS EEPROM content modifying or for debug purposes. The signals LMS_I2C_SCL, LMS_I2C_DATA connected to FPGA Bank 2 (VDIO_LMS_FPGA; 2.5V).
Table 2. RF transceiver (LMS7002) digital interface pins
Chip pin (IC1) Chip reference (IC1) Schematic signal name FPGA pin FPGA I/O standard Comment
E5 xoscin_tx TxPLL_CLK - 1.8V Connected to 40.00 MHz clock
AG31 DIQ1_D0 LMS_DIQ1_D0 M12 2.5V
AF30 DIQ1_D1 LMS_DIQ1_D1 N12 2.5V
AF34 DIQ1_D2 LMS_DIQ1_D2 N10 2.5V
AE31 DIQ1_D3 LMS_DIQ1_D3 L10 2.5V
AD30 DIQ1_D4 LMS_DIQ1_D4 M10 2.5V
AC29 DIQ1_D5 LMS_DIQ1_D5 M13 2.5V
AE33 DIQ1_D6 LMS_DIQ1_D6 N9 2.5V
AD32 DIQ1_D7 LMS_DIQ1_D7 N8 2.5V
AC31 DIQ1_D8 LMS_DIQ1_D8 M7 2.5V
AC33 DIQ1_D9 LMS_DIQ1_D9 N7 2.5V
AB30 DIQ1_D10 LMS_DIQ1_D10 M9 2.5V
AB32 DIQ1_D11 LMS_DIQ1_D11 N6 2.5V
AM24 xoscin_rx RxPLL_CLK - 1.8V Connected to 40.00 MHz clock
H30 DIQ2_D0 LMS_DIQ2_D0 M2 2.5V
J31 DIQ2_D1 LMS_DIQ2_D1 M4 2.5V
K30 DIQ2_D2 LMS_DIQ2_D2 M1 2.5V
K32 DIQ2_D3 LMS_DIQ2_D3 J1 2.5V
L31 DIQ2_D4 LMS_DIQ2_D4 N2 2.5V
K34 DIQ2_D5 LMS_DIQ2_D5 K1 2.5V
M30 DIQ2_D6 LMS_DIQ2_D6 L2 2.5V
M32 DIQ2_D7 LMS_DIQ2_D7 J2 2.5V
N31 DIQ2_D8 LMS_DIQ2_D8 N4 2.5V
N33 DIQ2_D9 LMS_DIQ2_D9 K2 2.5V
P30 DIQ2_D10 LMS_DIQ2_D10 L5 2.5V
P32 DIQ2_D11 LMS_DIQ2_D11 L4 2.5V
D28 SEN FPGA_SPI_LMS_SS J5 2.5V SPI interface
C29 SCLK FPGA_SPI_SCLK K5 2.5V SPI interface
F30 SDIO FPGA_SPI_MOSI J7 2.5V SPI interface
F28 SDO FPGA_SPI_MISO J6 2.5V SPI interface
D26 SDA LMS_I2C_SDA N5 2.5V Connected to EEPROM
C27 SCL LMS_I2C_SCL M5 2.5V Connected to EEPROM

4.2 USB 3.0 controller

Software controls LimeSDR-Mini board via the USB3 microcontroller (FTDI USB 3.0 to FIFO interface bridge chip FT601 [link]). The controller signals description showed below:

  • FT_D[31:0] – FTDI 32-bit data interface is connected to FPGA.
  • FT_TXEn, FT_RXFn, FT_SIWUn, FT_WRn, FT_RDn, FT_OEn, FT_BE[3:0] – FTDI interface control signals.
  • FT_CLK – FTDI interface clock. Clock from FTDI is fed to FPGA.

In the table below are listed USB3.0 controller (FTDI) pins, schematic signal name, FPGA interconnections and I/O standard.

Table 3. USB3 controller (FTDI) pins
Chip pin (IC6) Chip reference (IC6) Schematic signal name FPGA pin I/O standard I/O standard
40 DATA_0 FT_D0 A2 3.3V
41 DATA_1 FT_D1 B6 3.3V
42 DATA_2 FT_D2 B3 3.3V
43 DATA_3 FT_D3 B5 3.3V
44 DATA_4 FT_D4 A3 3.3V
45 DATA_5 FT_D5 B4 3.3V
46 DATA_6 FT_D6 E6 3.3V
47 DATA_7 FT_D7 A4 3.3V
50 DATA_8 FT_D8 B12 3.3V
51 DATA_9 FT_D9 H8 3.3V
52 DATA_10 FT_D10 E9 3.3V
53 DATA_11 FT_D11 B2 3.3V
54 DATA_12 FT_D12 D9 3.3V
55 DATA_13 FT_D13 J9 3.3V
56 DATA_14 FT_D14 A9 3.3V
57 DATA_15 FT_D15 H9 3.3V
60 DATA_16 FT_D16 A7 3.3V
61 DATA_17 FT_D17 F8 3.3V
62 DATA_18 FT_D18 A6 3.3V
63 DATA_19 FT_D19 E10 3.3V
64 DATA_20 FT_D20 A5 3.3V
65 DATA_21 FT_D21 F9 3.3V
66 DATA_22 FT_D22 E8 3.3V
67 DATA_23 FT_D23 A8 3.3V
69 DATA_24 FT_D24 K11 3.3V
70 DATA_25 FT_D25 K12 3.3V
71 DATA_26 FT_D26 J12 3.3V
72 DATA_27 FT_D27 G12 3.3V
73 DATA_28 FT_D28 L13 3.3V
74 DATA_29 FT_D29 G13 3.3V
75 DATA_30 FT_D30 J13 3.3V
76 DATA_31 FT_D31 H13 3.3V
58 CLK FT_CLK G9 3.3V
4 BE_0 FT_BE0 B11 3.3V
5 BE_1 FT_BE1 C12 3.3V
6 BE_2 FT_BE2 A12 3.3V
7 BE_3 FT_BE3 B13 3.3V
8 TXE_N FT_TXEn C13 3.3V
9 RXF_N FT_RXFn A12 3.3V
10 SIWU_N FT_SIWUn - 3.3V 10k pull up
11 WR_N FT_WRn E12 3.3V
12 RD_N FT_RDn D12 3.3V
13 OE_N FT_OEn F12 3.3V

4.3 Indication LEDs

LimeSDR-Mini board comes with one dual colour (red and green (RG)) indication LED. This LEDs can be soldered on the top (LED1) or on the bottom (LED2). By default, LED1 is populated and LED2 is unpopulated.

Figure 5. LimeSDR-Mini indication LEDs

LEDs are connected to FPGA to the same lines and their function can be changed.

4.4 Low speed interfaces

LimeSDR-Mini board low speed interfaces are presented in Figure 6. The latter block diagrams depict the main ICs, corresponding IC pin numbers, data buses and serial protocol addresses.

Figure 6. Low speed interfaces block diagram

There are several SPI interfaces with their slave devices:

  • FPGA_SPI: this SPI interface are connected to FPGA and slave devices can be accessed by transferring data to internal FPGA NIOS CPU. This bus has these slave devices RFIC (IC1) and DAC (IC9).
  • FPGA_QSPI: this SPI interface is connected to Quad SPI flash memory (IC11).
  • Internal FPGA SPI module: FPGA has its own SPI module and can be controlled as regular SPI device. By using FPGA SPI it is possible to control FPGA modes etc.
  • FPGA_I2C: used to control external clock temperature sensor and EEPROM on LimeSDR-Mini board.

In the tables below are listed FPGA_SPI pins, schematic signal names, FPGA interconnections and I/O standards.

Table 4. FPGA_SPI interface pins
Schematic signal name FPGA pin I/O standard Comment
FPGA_SPI_SCLK K5 2.5V (3.3V) Serial Clock (FPGA output)
FPGA_SPI_MOSI J7 2.5V (3.3V) Data (FPGA output)
FPGA_SPI_MISO J6 2.5V (3.3V) Data (FPGA input)
FPGA_SPI_LMS_SS J5 2.5V (3.3V) IC1 (LMS7002) SPI slave select (FPGA output)
FPGA_SPI_DAC_SS K8 2.5V (3.3V) IC9 SPI slave select (FPGA output)

In the tables below are listed FPGA_QSPI pins, schematic signal names, FPGA interconnections and I/O standards.

Table 5. FPGA_QSPI interface pins
Schematic signal name FPGA pin I/O standard Comment
FPGA_QSPI_SCLK F1 1.8V Serial Clock (FPGA output)

In the tables below are listed FPGA_I2C interface slave devices and their other information.

Table 6. FPGA_I2C interface pins
I2C slave device Slave device I2C address I/O standard Comment
IC8 Temperature sensor 1 0 0 1 0 0 0 RW 3.3V LM75
IC10 EEPROM 1 0 1 0 0 0 0 RW 3.3V M24128

8 GPIOs from FPGA are connected to 10 pin 0.05” header. Additional 2 pins are dedicated for power. Another 2 GPIOs are connected to 5 header on the board edge. In the tables below are listed FPGA_GPIO (J5) and FPGA_EGPIO (J6) information.

Table 7. FPGA GPIO connector (J5) pins
Connector pin Schematic signal name FPGA pin I/O standard Comment
1 FPGA_GPIO0 A11 3.3V
2 FPGA_GPIO1 B10 3.3V
3 FPGA_GPIO2 C10 3.3V
4 FPGA_GPIO3 D11 3.3V
5 FPGA_GPIO4 E13 3.3V
6 FPGA_GPIO5 F13 3.3V
7 FPGA_GPIO6 F10 3.3V
8 FPGA_GPIO7 G10 3.3V
9 GND - Ground pin
10 - Selectable power net (3.3V or 5V). Default 3.3V
Table 8. FPGA EGPIO connector (J5) pins
Connector pin Schematic signal name FPGA pin I/O standard Comment
1 GND Ground pin
4 VCC3P3 3.3V Power net (3.3V)
5 VCC1P8 1.8V Power net (1.8V)

4.5 Board Temperature Control

LimeSDR-Mini has integrated temperature sensor which controls FAN to keep board in operating temperature range. FAN must be connected to J10 (0.1” pitch) connector. FAN control voltage is 5V, but it can be changed to 3.3V by resistors. Fan will be turned on if board will heat up to 55°C and FAN will be turned off if board will cool down to 45°C. By default temperature sensor is unpopulated and FAN is always on.

Figure 7. FAN control temperature hysteresis

4.6 Clock Distribution

LimeSDR-Mini board clock distribution block diagram is presented in Figure 8. LimeSDR-Mini board has onboard 40.00 MHz VCTCXO that is reference clock for LMS and FPGA PLLs.

Figure 8. LimeSDR-Mini board clock distribution block diagram

VCTCXO frequency can be tuned by using DAC (IC8). Buffered VCTCXO clock is connected to RF transceiver, FPGA. Buffered VCTCXO clock is also connected to connector J9 (REF_CLK_OUT) and can be fed to external hardware for synchronisation. VCTCXO can be disconnected from clock buffer input (remove R59 and solder R62) and external reference clock can be supplied from connector J8 (REF_CLK_IN).

Table 9. LimeSDR-Mini clock pins
Source Schematic net name I/O standard FPGA pin Description
External REF_CLK_IN External reference clock input
Board Board 2.5V (3.3V) Buffered reference clock output
Clock buffer (IC7) LMK_CLK 2.5V (3.3V) H6 Buffered reference clock output
RF transceiver (IC1) RxPLL_CLK 2.5V (3.3V) Buffered reference clock output
TxPLL_CLK 2.5V (3.3V) Buffered reference clock output
LMS_MCLK1 2.5V (3.3V) G5
LMS_FCLK1 2.5V (3.3V) L3
LMS_MCLK2 2.5V (3.3V) H4
LMS_FCLK2 2.5V (3.3V) M3
USB3.0 controller FT_CLK 3.3V G9 100 MHz

External clock notes. External clock capabilities on LimeSDR-Mini board are defined by LMK00105 clock buffer specification. User must ensure voltage levels are in the range of LMK00105 capabilities. Ideally, a phase detector circuitry should be used to synchronize on board TCXO to the external clock but there simply is no space on LimeSDR-Mini for this functionality. Hence decision was made just to provide an input to LMK clock buffer for external clock connection. This means that user should pay attention on how external signal is connected, ensure proper voltage levels etc. If you supply external clock signal from signal generator, signal level should be around 10dBm. Note please, that LMK clock buffer expects positive voltage amplitude, while your generator may supply +/- voltage.

The proper way to supply the external reference clock: supply external clock firstfirst and then turn the board on. This is the only way to have proper operation of the board with external clock. If frequency is changed on the fly, CPU inside of FPGA gets messed up hence no control over the board.

4.7 Power Distribution

LimeSDR-Mini board is powered from USB port. LimeSDR-Mini board power delivery network consists of different power rails with different voltages, filters, power sequences. LimeSDR-Mini board power distribution block diagram is presented in Figure 9.

Figure 9. LimeSDR-Mini v1.2 board power distribution block diagram