Project details

Name: GECKObiomed
Revision: 1.1
Development status: stable
Compatibility: GECKO3 / GECKO4

The GECKO-biomed AddOn is a signal processing education board which uses the micolink platform . With the GECKO-biomed a 3-wire ECG can be recorded and displayed. A capacitive touch wheel serves as user input device.

DO NOT USE USB-POWERED ON GECKO4. It may destroy the power supply of your device!


Make sure to have distance keeper mounted between the GECKOmain and the GeckoBiomed while using the board to prevent damages on the connectors!

ECG Front-End

To record ECG signals the ADS1194 is used. The ADS1194 includes an analog front end as well as an 16-Bit ADC and needs a minimum of external components.

Features of ADS1194 (Datasheet):

  • 4 Low-Noise Programmable Gain Amplifiers
  • Programmable Gain: 1,2,3,4,6,8 or 12
  • 4 16-Bit ADCs
  • Data Rate: 125 SPS up to 8 kSPS
  • CMRR: -105dB
  • Built-In Right Leg Drive Amplifier, Lead-Off Detection, WCT, Test Signals
  • SPI Data Interface

The development of the sensing circuit was done with the ADS1198 evaluation kit (Datasheet). The schematic which is provided in the datasheet was copied and only slightly adapted. The GECKO-biomed AddOn Board uses only 1 Channel of the ADS1194.


To record the ECG-Signal a 3 wire cable is used. The cable is connected to the GECKO-biomed by a 3.5mm audio jack.

Touch Buttons

As user input unit capacitive touch buttons are used. The buttons are made by copper layers on the PCB. The used sensing principle is called sigma-delta capacitive sensing.
Find detailed information in this paper: Delta Sigma

OLED Display

To display the ECG-signal a 160 x 128 OLED screen is used:

  • Module Name: DD-160128FC-2A
  • Driver IC: SEPS525
  • Mode: OLED RGB
  • Colors: 262 k
  • Data Interface: 6800-/8080-Series MPU
  • Control Interface: SPI
  • Size: 1.69''
  • Resolution: 160 x 128
  • Used Voltage Booster: TPS61080


The GECKO-biomed has 4 LED's which are mounted on the backside of the PCB. The LED's can be used as optical feedback.

PCB design was done by altium designer ECAD. The design files are located in the following directory:


For the next revision the power pins on the GPIO 1 have to be adapted to the new specification.


System Bus

On GECKO-biomed only system bus 1 is used. For this reason GECKO-biomed can be used with GECKO3main and GECKO4main.


Do not Power the Gecko and the Biomed board over USB only! It will destroy your device.
For safety reasons all used GECKO modules have to be powered by battery when recording/displaying an ECG! Don't use an AC wall adapter!

To power a GECKO stack by battery use the GECKO-robot or use a battery powered GECKO-simple!

Component 3.3 V 3 V 18 V
OLED Logic
OLED Driver
Touch Buttons
ADS1194 Analog
ADS1194 Interface

For 3.3V the +3.3V line from the GECKO system bus 1 is used. 3V and 18V are generated out of VBAT.

PCB Layout

Final Result


GECKO-biomed only uses system bus 1. On this bus the signals on GECKO3main and GECKO4main are pin compatible. Select the correct .ucf file for the particular GECKO-main version.

GECKO3main: geckobiomed_gecko_3.ucf

GECKO4main: geckobiomed_gecko_4.ucf

Pin Name GECKO3main FPGA GECKO4main FPGA Description
1 GND - - System GND
2 GND - - System GND
4 PHI2 AF19 AC25 Switch Signal N-FET
5 GND - - System GND
6 PHI1 AE20 AC26 Switch Signal P-FET
8 GND - - System GND
11 Q_Touch_1 AD19 Y25 Button 1 discharge
12 GND - - System GND
13 Q_Touch_2 AE18 Y26 Button 2 discharge
14 D_Touch_1 AD25 W25 Button 1 output
15 Q_Touch_3 AE23 W26 Button 3 discharge
16 D_Touch_2 AC21 V25 Button 2 output
17 Q_Touch_4 AF22 U26 Button 4 discharge
18 D_Touch_3 AC22 U25 Button 3 output
19 Q_Touch_5 AE22 T26 Button 5 discharge
20 D_Touch_4 AB20 T25 Button 4 output
21 LED4 AB17 R26 LED 4
22 D_Touch_5 AB19 R25 Button 5 output
23 LED3 AC19 P26 LED 3
25 LED2 AA25 AB23 LED 2
27 LED1 AB25 U20 LED 1
29 GND - - System GND
30 GND - - System GND
33 GND - - System GND
34 GND - - System GND
35 VBAT - - Battery Power
36 VBAT - - Battery Power
37 VBAT - - Battery Power
38 VBAT - - Battery Power
39 VBAT - - Battery Power
40 VBAT - - Battery Power
41 GND - - System GND
42 GND - - System GND
43 GND - - System GND
45 GND - - System GND
46 GND - - System GND
47 3V3 - - System 3.3 V supply
48 3V3 - - System 3.3 V supply
49 3V3 - - System 3.3 V supply
50 3V3 - - System 3.3 V supply
51 3V3 - - System 3.3 V supply
52 3V3 - - System 3.3 V supply
53 GND - - System GND
54 GND - - System GND
56 GND - - System GND
59 GND - - System GND
60 GND - - System GND
69 OLED_BL_EN W25 J25 OLED Backlight Enable
71 OLED_WRB W22 H25 OLED Write or Read/Write select
72 OLED_RDB V22 D26 OLED Read or Read/Write enable
73 OLED_CSB W21 D25 OLED Chip Select
74 OLED_RS U22 N20 OLED Data/Command select
75 OLED_D9 V21 N19 OLED Image Data 9
76 OLED_D10 R20 M20 OLED Image Data 10
84 OLED_D11 U20 U21 OLED Image Data 11
85 OLED_D12 T20 V23 OLED Image Data 12
86 OLED_D13 R22 U22 OLED Image Data 13
87 OLED_D14 R21 V24 OLED Image Data 14
88 OLED_D15 P22 T21 OLED Image Data 15
89 GND - - System GND
90 GND - - System GND
91 OLED_D16 P21 U23 OLED Image Data 16
92 OLED_D17 N22 T22 OLED Image Data 17
93 OLED_PS N21 U24 OLED Select Interface Type
94 OLED_CPU K22 R21 OLED Select CPU Type
95 OLED_ENABLE L23 T23 OLED Video Enable
96 OLED_DOTCLK T19 R22 OLED Dotclock
97 OLED_HSYNC R19 R24 OLED Horizontal Sync Input
98 OLED_VSYNC P20 P21 OLED Vertical Sync Input
99 OLED_VSYNCO P19 P23 OLED Vertical Sync Output
103 ECG_SPI_DRDY M19 N24 ECG Data Ready
104 ECG_RESET L20 N21 ECG Chip Reset
105 ECG_SPI_START L19 N23 ECG Start Conversion
106 ECG_PWDN L25 M22 ECG Power Down
115 ECG_SPI_CLK B10 J24 ECG SPI clock input
116 ECG_SPI_IN B11 K21 ECG SPI data in
117 ECG_SPI_OUT A10 J23 ECG SPI data out
118 ECG_SPI_CS A11 J22 ECG SPI chip select
119 GND - - System GND
120 GND - - System GND

Unlisted pins are unused

GECKO system bus 2 is unused.

The GeckoBiomed has its own Matlab library. It can be started over the Menu (Applications→Microlab→Others→GeckoBiomed) in your desktop environment.

  • gecko-addons/gecko-biomed.txt
  • Last modified: 2021/12/20 10:49
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