Jun 112016

So, I’ve built the controller. The design was pretty simple. Using an ATTiny24A, I’d monitor the voltages of the battery and two power inputs, and code would decide which input to use, if any. It also could use the in-built temperature sensor to control cooling fans. This is the schematic I knocked up this morning.

The values of most resistors are not critical. I found I needed 1kOhm resistors into the bases of the transistors as the MCU was not happy driving them directly. The transistors I’m using are BC547Bs controlling AUIRF4905 MOSFETs.

The only components that are critical are the voltage dividers on the ADC inputs. I’ll be using the built-in 1.1V reference in the MCU as that’s what’s needed for the temperature sensor anyway.

This was a bit of an exercise in reviving old brain cells as it’s been some time since I’ve done a proper PCB myself. This is a one-off prototype with mostly larger components, so no point in getting boards fabricated. I did it the old fashioned way, using a dalo pen then etching in a bath of Ferric Chloride.

That gives you an idea of what the board looked like prior to population. The underside was covered with tape to prevent it from being etched. It took a while, and I think I could have upped the concentration of the solution a bit, since it did leave some tracks un-etched.

Perhaps my solution is getting a little old too… the logo on the bottle really dates it. I found I had to attack the gaps between some tracks with a knife since the etchant didn’t quite get it all.

There are no tracks on the bottom, it’s just one piece of un-etched copper, to act as a ground plane. I guess the construction style is a cross between Manhattan and groundplane (dead-bug) construction. The constructed board looks like this.

I’m not sure what all the LEDs will be doing at this point. Three share pins with the ICSP header, which means they flash as the board is being programmed… useful for troubleshooting ICSP issues. The IC socket is a cheap 14-pin one, I just bent the pins to mount it flush to the board. The 10uF tantalum on the output of the 5V PSU is possibly a 10V one. Where the electrolytic is, is where I had the 330uF tantalum mounted, and it went bang when I gave it 12V.

I tried the following program on the board which just steps through all the LEDs and MOSFETs:

/* board.h */
/* LEDs */
#define LED_U1_BIT		(1 << 7)
#define LED_MOSI_BIT		(1 << 6)
#define LED_MISO_BIT		(1 << 5)
#define LED_SCK_BIT		(1 << 4)
#define LED_U0_BIT		(1 << 3)
/* MOSFETs */
#define FET_MAINS		(1 << 0)
#define FET_SOLAR		(1 << 1)
#define FET_FAN			(1 << 2)
/* test.c */
#include <avr/interrupt.h>
#include <util/delay.h>
#include <stdint.h>
#include "board.h"
uint8_t heartbeat = 10;
int main(void) {
	PORTA = 0;
	PORTB = 0;
	/* Test sequence */
	while (1) {
		PORTA = LED_U0_BIT;	_delay_ms(1000);
		PORTA = LED_U1_BIT;	_delay_ms(1000);
		PORTA = LED_MOSI_BIT;	_delay_ms(1000);
		PORTA = LED_MISO_BIT;	_delay_ms(1000);
		PORTA = LED_SCK_BIT;	_delay_ms(1000);
		PORTA = 0;
		PORTB = FET_MAINS;	_delay_ms(1000);
		PORTB = FET_SOLAR;	_delay_ms(1000);
		PORTB = FET_FAN;	_delay_ms(1000);
		PORTB = 0;
	return 0;

That seems to prove the hardware is alive, and now I just have to get the software working. Now to try out the toolchain I built!


May 162011

This weekend just gone I was at Imbil helping out with the International Rally of Queensland, reporting scores for the car rally there.  This was my first look at packet radio in action.  Prior to this I had enabled the amateur radio options in the kernels I built, but never tried actually hooking radio to computer.  I shall be posting some notes on how I got this working…

zhouman ~ # uname -a
Linux zhouman #2 Wed Oct 13 00:42:58 EST 2010 mips64 ICT Loongson-2 V0.3 FPU V0.1 lemote-yeeloong-2f-8.9inches GNU/Linux
zhouman ~ # ifconfig sm0
sm0 Link encap:AMPR AX.25 HWaddr VK4MSL
inet addr: Bcast: Mask:
RX packets:365 errors:0 dropped:0 overruns:0 frame:0
TX packets:36 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:24236 (23.6 KiB) TX bytes:6850 (6.6 KiB)

zhouman ~ # mheard
Callsign Port Packets Last Heard
VK4EA-9 sm0 6 Mon May 16 17:59:12
VK4NRL-9 sm0 1 Mon May 16 17:58:40
VK4VP-1 sm0 8 Mon May 16 17:58:38
VK4RAI-3 sm0 9 Mon May 16 17:57:58
VK4TIM-9 sm0 14 Mon May 16 17:57:56
VK4TDI-1 sm0 2 Mon May 16 17:57:39
VK4DC-1 sm0 15 Mon May 16 17:57:07
VK4TEC-9 sm0 120 Mon May 16 17:56:08
VK4FY-1 sm0 18 Mon May 16 17:54:38
VK4RMO-3 sm0 1 Mon May 16 17:54:33
VK4RGC-3 sm0 3 Mon May 16 17:52:48
VK4RC-1 sm0 8 Mon May 16 17:51:29
VK4FIL-1 sm0 4 Mon May 16 17:46:44
VK4RIL-13 sm0 4 Mon May 16 17:45:43
VK4RBR-3 sm0 5 Mon May 16 17:42:59
VK2RDO-3 sm0 2 Mon May 16 17:41:19
VK4RRC-13 sm0 3 Mon May 16 17:36:39
VK2JUB-1 sm0 2 Mon May 16 17:34:44
VK4BNQ-1 sm0 1 Mon May 16 17:26:58
VK4LDA-9 sm0 2 Mon May 16 17:24:59
VK2POO-9 sm0 9 Mon May 16 17:21:24
VK2XFL-9 sm0 1 Mon May 16 17:21:09
VK4RSR-3 sm0 1 Mon May 16 17:20:04
VK4IE sm0 1 Mon May 16 17:15:04
VK4ALJ-3 sm0 1 Mon May 16 17:15:00
VK4HPW-9 sm0 5 Mon May 16 17:13:23
zhouman ~ #

Set-up consisted of:
Linux kernel on Lemote Yeeloong, latest soundmodem driver, Yaesu FT-897D, homebrew interface cable plugged into Yeeloong’s onboard sound card, USB serial driving BC547 in interface cable for PTT.

zhouman ~ # cat /etc/ax25/soundmodem.conf
<?xml version="1.0"?>
<configuration name="FT897-D">
<chaccess txdelay="150" slottime="100" ppersist="40" fulldup="0" txtail="10"/>
<audio type="alsa" device="plughw:0,0" halfdup="0" capturechannelmode="Mono"/>
<ptt file="/dev/ttyUSB0"/>
<channel name="Channel 0">
<mod mode="afsk" bps="1200" f0="1200" f1="2200" diffenc="1"/>
<demod mode="afsk" bps="1200" f0="1200" f1="2200" diffdec="1"/>
<pkt mode="MKISS" ifname="sm0" hwaddr="VK4MSL" ip="" netmask="" broadcast=""/>
zhouman ~ #

I’ve shut it down for now, but I’ll give it a bit more work on 145.175MHz tomorrow. Once I get something working, I might set something up using the O2 or one of the Fulongs (probably the latter) and see about getting soundmodem back into Gentoo.

Update: After hand-editing the ebuild to enable APRS support, I can successfully report that not only is soundmodem working, but so is Xastir on my Yeeloong, as can be seen on aprs.fi.