- Tytera MD-380(V)(G)
- Tytera MD-390(V)(G)
- Retevis RT3
The suffix "V" denotes the VHF version of a MD-380/390, while its absence denotes an UHF one.
The suffix "G", instead, denotes the presence of a GPS module.
Model variants
- With GPS: with JumpStar JS-H210 module on display/keyboard PCB
- Without GPS: no module footprint present on display/keyboard PCB
- Display: 160x128 color TFT
- Frequency range
- VHF: 136.000-174.000
- UHF: 400.000-480.000
- 8MHz crystal as PLL reference
- Sytem clock frequency: 72MHz
- APB1 bus clock frequency: 36MHz
- APB2 bus clock frequency: 72MHz
Here are summarised the differences between the GPIO connections reported on the schematic of the MD-380 UHF and their real function, obtained by software and hardware reverse engineering.
ADC2 samples the voltage on PC3 pin (2T/5T signal), data is drained via DMA2_Stream and conversion is triggered by TIM3 trigger output signal, on both rising and falling edges.
ADC2 samples the voltage on PA2 pin (QT_DQT_IN signal), conversion is triggered by software in a function at address 0x0803e45e and data is collected and processed either in the function at address 0x0803eb2a or in the function at address at 0x0803e47e. The function starting the conversion and then processing the acquired sample is called from TIM7 interrupt handler.
TIM3 is configured in compare mode with the trigger output signal sending a positive pulse when the CC1IF flag is to be set (even if it was already high), as soon as a capture or a compare match occurred. Output compare channel 1 is set to toggle mode, its output toggles when TIM3_CNT is equal to TIM3_CCMR1. Prescaler is set to 9 and reload value is 0x2CF (719 decimal). CCMR1 register is set to 0x359 (857 decimal). Given an APB1 clock frequency of 36MHz, timer tick frequency is 3.6MHz and timer update frequency is 5kHz.
TIM7 is configured with a prescale value of 7 and a reload value of 0x3e7 (999 decimal). Given an APB1 clock frequency of 36MHz, timer tick frequency is 4.5MHz and timer update frequency is 4.5kHz. The interrupt handler is called once per each update and controls CTCSS encoding and decoding.
The decoded DMR audio output from the HS_C5000 LINE_OUT (Pin 10) passes through op amp U203 and is routed as the input of the volume knob (VOL_OUT on the schematic). The volume pot controls the signal level sent to Input 1 (Pin 7) of the audio amp U204. In FM mode, the demod audio output (AF_OUT) is passed through U102 op amps before routed to the volume knob input (VOL_OUT), so it too is controlled by the volume pot.
PWM out from STM PC8 (Pin 65) is used to provide beeps and startup tones to the speaker that are not controlled by the volume knob. The output signal from this pin passes through a series of resistors and a cap R339,R340, C337, R341. The schematic indicates that this signal is sent to the volume pot (VOL_OUT) but this is not correct. It is connected directly to pin 7 of U204 (input 1 of audio amp) completely bypassing the volume knob and where it is mixed with the signals connected to VOL_OUT and were passed though the volume pot.
PWM out from STM PC8 (Pin 65) is used in OpenRTX to output the decoded M17 audio to the speaker during RX, as well as generate M17 encoded audio sent to the modulator during TX (2T/5T/DTMF_OUT). During TX, the M17 encoded audio on 2T/5T/DTMF_OUT is sent into the HR_C5000 Pin 5 which then generates the MOD1 and MOD2 signals out of pin 74 and 75 and into the VCO. The audio path in FM mode remains unchanged.