写频器

自制通用电台写频器时间:2009-03-06 来源: 作者: 点击：2949 字体大小:【】其实给对讲机写频时，写频器起到的作用就是对电平的转换,通俗点讲就是把电脑发出的信息转换成对讲机能读懂的信息,就如翻译一样.下面我们来看看两张写频器的电路图，这两个图都是用了MAX232这个电脑串口电平转换专用芯片，它有着兼容性好、稳定性好、外围电路简单、容易制作等优点。

图一：这个是给部分要接4条线的手台、车台写频的电路。

如TK3107等要接TXD（发送）、RXD（接收）、GEN（接地）、+5V，这四条线的机器。

图二：这个是写需要接DATA（总线）、GEN（接地）、+5V这三条线的机器，如GP88、GP88S等。

（其中发射和接收就用一个二极管或者三极管进行切换）首先大家需要采购回以下配件:MAX232芯片一片约6元18脚IC座一个约4毛钱50伏10微法的电解电容4个约1毛一个RS232母头一个(插到电脑COM口上的) 约2.5元一套(带外壳) 1N4148二极管一个约1毛一个USB延长线一条（1.5米或者更长）约2元一条万能板一小块（半个巴掌大足够）约1块钱便宜的配件可以多买几个，以备掉了、坏了或者猫叼了、狗啃了等等，呵呵！！（以上价格是本地的零售价格，也许和你们当地有差异，但出入不大，小心上JS的当。

）同时自己还需要准备些工具如烙铁，焊锡，松香，起子等工具和材料。

关于芯片等配件的引脚请看下面的几张图片，只要细心的对照着焊接，不出错的话不用调试（也没有什么调试的）就可以使用。

这个就是"传说"中的MAX232芯片啦IN4148的正负极判别:电容的正负极判别:RS232接头是这个样子的,还有它的引脚排列方式:制作过程：取USB延长线，剪掉母头（就是不能插进电脑USB口的那头），然后在距离公头（当然是剩下的那头啦）约20厘米的地方也剪掉，剩余下来的那段4芯线就用作连接写频器和RS232插头之间的导线咯。

下一步就是先把IC座焊在万能板上，然后再焊接外围的4个电容和二极管，接好导线，最后把MAX232芯片插上就可以了。

我这里考虑用IC座的原因是防止搞错脚位而多次拆焊IC导致损坏，而且芯片日后还可以拔下用于其他电路中。

如果你认为不需要这样做的话也可以省掉IC座而直接把芯片焊在电路板上。

大家如果用IC座的话仔细看座子上的一头是不是有个半圆形的小缺口,这个是和芯片上那个缺口对应的(注意看我上面的MAX232那张图画红圈的地方).这个就是用来标记方向的,以防将芯片插反,大家做的时候注意一下就好.如果实在不懂得焊接就找个朋友代劳吧，毕竟是个非常简单的电路，很容易搞掂的。

还要说明一点，+5V电源取自USB口，就是用刚才剪下来的那段约20厘米长的公头线，把里面红色的那根导线与写频器的+5V相连接就可以了，UBS口的其他几根千万别接，也别让他们之间短路，包好就行，否则USB口烧掉了别怪我。

贴个PCB图让大家参考一下线路是怎么走的.注意这个图是PCB图,就是电路板焊接的这一面,并且注意对照好上面的引脚,别弄错了.最后上成品的图：带供电方式的图GM950i车台接口定义GM350/GM600/GM950/MCX600 Mobiles--------------------------------------------------------------------------------第七针.....是写频的针脚...上传的图像General InformationThese radios should all be similar to each other. If there are any significant differences, please email us.The MCX600 is the Asia version of the GM600 which is the MPT version of theGM350/950.The GM350 has its own RSS and are a PL/Singletone only version of the GM950. They come in two flavours, 4 channels without LCD and 128ch with LCD. Out of band is similar to the GP320/340 series.The GM950 also has its own RSS. They have similar features to GM350 but also have SELECT-5. It comes in 4 flavours, 4 channels w/o LCD, 128 ch with LCD, 128ch with handheld control mic (HHCM), and 128ch with full keypad (eg. 0-9 + * and #). Same Out of Band as for the GM350.If you are looking for the the pinout of the GTF377A "Front to Back" cable, the pinout is:RJ45 8pin 16pin Accessory Function(Acc)7 Orange 6 BUS+4 Green 7 Ground1 Brown 13 SW B+3 Yellow 14 HookThe above cable lets you program from the accessory connector instead of the mic connector. It is an RJ45 female that is wired to a 16pin accessory connector using the above schematic. You plug this cable on the end of the standard programming cable (RJ45) and then into the accessory plug on the radio for rear programming (in the event you don't have a head on the radio to program through the mic jack).Accessory Connector DetailsThe 16-pin accessory connector pin functions for the GM950 N3/N4 are as follows:Pin Name Type1 SPKR- Analog O/P2 Ext. Mic Audio Analog I/P3 GP1 Digital I/P4 GP2 Digital O/P5 Flat TX Audio Analog I/P6 BUS+ Digital I/O7 GND Ground8 GP3 Digital O/P9 GP4 Digital I/P10 Ignition Sense Digital I/P11 RX Audio Analog O/P12 GP5 Digital I/O13* SW B+ Sense Analog O/P14 Hook Digital I/P15 RSSI Analog O/P16 SPKR+ Analog O/P*Factory default SWB+PIN 1Speaker- Audio. Speaker- and Speaker+ (PIN 16) are used to connect an external speaker. The audio PA is a bridge amplifier with a minimum load resistance of 3.2 ohms. The internal speaker can be easily disabled by removing the control head. Disconnect the internal speaker and assemble the control head back to the radio. PIN 2Microphone audio. This microphone signal input is common with the microphone singal input on the microphone connector and is connected to the microphone path input of the ASFIC. The nominal input level is 80mV for 60% deviation. The DC impedence is 1100 ohms and the AC impedence is 1000 ohms. Note: Only one microphone should be connected at any one time.PIN 3internal option connector (J0102:7). The RSS details which functions may be assigned to this pin by the codeplug. The primary use for this pin will be external PTT. (See Note 1).PIN 4General Purpose 2 (GP2). This is a digital output only. The RSS details whuch functions may be assigned to this pin by the codeplug. The primary use for this pin is as external alarm output. (See Note 3).PIN 5Flat TX Audio. This input is for injecting signals into the transmit path that should not be filtered, e.g. the output of a modem. The nominal input level is 150 mVRMS for 60% deviation. The impedence is greater than 25 kohms.PIN 6BUS+. This connects to the radio's SCI serial bus which is used for programming and tuning the radio. This line is also available at the microphone connector Pin 7. PIN 7Ground. Used as a ground for both analog and digital signals.PIN 8General Purpose 3 (GP3). This is a digital output and is also available on the internal option connector (J0103:7). The RSS details which functions may be assigned to this pin by the codeplug. (See Note 2). This output is shared with the serial bus data line. It can be used as a normal output, but will be overridden by serial data when the programming lead is plugged in. To restore general purpose output operation, the programming lead must be removed and the radio turned off, then on again. PIN 9General Purpose 4 (GP4). This is a digital input only. The RSS details which functions may be assigned to this pin by the codeplug. (See Note 1). This is a special input that will force the radio to turn on when it is grounded. This can be used for any input function, but is usually used for emergency.PIN 10Ignition Sense. Connecting this line to the ignition line of the vehicle will automatically turn the radio on when the ignition of the vehicle is turned on. When the ignition is connected, the radio cannot be turned off as long as the ignition is active. When this line is at 0V or is not connected, power on/off is under manual control. Resistor R0423, 4.7 kohm, which is not fitted as standard will cause the radio to be permanently on whenever 12 V is connected to the main power connector.PIN 11RX Audio Discriminator. The signal routed to this pin is controlled by ASFIC and gives continuous discriminator audio. For discriminator audio, the normal output level is 330 mVRMS for 60% deviation. The impedence is 600 ohms.PIN 12internal option connector (J1003:3). The RSS details which functions may be assigned to this pin by the codeplug. (See Note 1 and Note 2).PIN 13Switched B+ Sense. The output of this pin may be configured by a solder link within the radio. Switched B+ is the default. The current limiting resistor R0455 default is 0 ohms, therefore, extreme care must be taken to avoid short circuiting this output to ground, which will damage the radio. The maximum continuous current allowed is 300 mA. A suitable external fuse must be installed into the lead to Pin 13 to avoid damage to the radio.PIN 14Hook. This port reads "0" when the microphone is on-hook, and "1" when the microphone is off-hook. It is assumed that the hook is a mechanical switch, so the software will always debounce this input. Also available on the microphone connector pin 3.PIN 15RSSI. Received Signal Strength Indication, buffered analog voltage.PIN 16Speaker+ Audio. Positive output of radio's PA (see PIN 1).Note 1: Digital Input4.7 kohm Internal Pull Up Resistor to +5 V,Maximum Input Voltage accepted as Low = 0.6 VMinimum Input Voltage accepted as High = 3.0 VNote 2: Digital Output4.7 kohm Internal Pull Up Resistor to +5 V,Maximum Current when Output Low = 10 mAMaximum Voltage when Output Low = 0.5 V @ 10 mANote 3: High Current Digital Output4.7 kohm Internal Pull UP Resistor to B+,Maximum Current when Output Low = 200 mAMinimum Voltage when Output Low = 1.7 V @ 200 mAMicrophone Connector DetailsPIN Name Type1 N/C2 N/C3 Mic Hook Digital I/P4 Ground Ground5 Mic Audio Analog I/P6 Mic PTT Digital I/O7 BUS+ Digital I/O8 Handset Analog O/P上传的图像14155．点火控制输入（10）由于GM950系列车载对讲机采用电子开关，因此在断电后，必需按电源开关触发接通对讲机内部电源。